Acquired Resistance to Third-Generation EGFR Tyrosine Kinase Inhibitors in Patients With De Novo EGFRT790M-Mutant NSCLC

IntroductionEGFR^T790M mostly exists subclonally and is acquired as the most common mechanism of resistance to EGFR tyrosine kinase inhibitors (TKIs). Nevertheless, because de novo EGFR^T790M-mutant NSCLC is rare, little is known on acquired resistance mechanisms to third-generation EGFR TKIs.MethodsAcquired resistance mechanisms were analyzed using tumor and plasma samples before and after third-generation EGFR TKI treatment in four patients with de novo EGFR^T790M-mutant NSCLC. Genetic alterations were analyzed by whole-exome sequencing, targeted sequencing, fluorescence in situ hybridization, and droplet digital PCR. MTOR^L1433S, confirmed for oncogenicity using the Ba/F3 system, was reproduced in H1975 cell lines using CRISPR/Cas9-RNP.ResultsOf seven patients with NSCLC with de novo EGFR^T790M/L858R mutation, four (LC1–4) who received third-generation EGFR TKIs acquired resistance after achieving a partial response (median = 27 mo, range: 17–48 mo). Novel MTOR^L1433S and EGFR^C797S/L798I mutations in cis, MET amplification, and EGFR^C797S mutation were identified as acquired resistance mechanisms to third-generation EGFR TKIs. The MTOR^L1433S mutation was oncogenic in Ba/F3 models and revealed resistance to osimertinib through AKT signaling activation in NCI-H1975 cells harboring the MTOR^L1433S mutation edited by CRISPR/Cas9 (half-maximal inhibitory concentration, 800 ± 67 nM). Osimertinib in combination with mTOR inhibitors abrogated acquired resistance to osimertinib.ConclusionsActivation of bypass pathways and the EGFR^C797S or EGFR^C797S/L798I mutation were identified as acquired resistance mechanisms to third-generation EGFR TKIs in patients with NSCLC with de novo EGFR^T790M mutation. In addition, MTOR^L1433S- and EGFR^L858R/T790M-mutant NSCLC cells were sensitive to osimertinib plus mTOR inhibitors.     

Comprehensive Analysis of EGFR-Mutant Abundance and Its Effect on Efficacy of EGFR TKIs in Advanced NSCLC with EGFR Mutations

IntroductionA qualitative detection method for EGFR mutations is not sufficient to guide precise targeted therapy in clinical practice. The aim of this study was to explore the relationship between the abundance of EGFR mutations and efficacy of EGFR tyrosine kinase inhibitors (TKIs).MethodsWe used the amplification refractory mutation system (ARMS) method optimized with competitive blockers and specific mutation quantitation (ARMS+) to quantitatively evaluate the abundance of EGFR mutations in 201 patients with advanced NSCLC. A cutoff value of the abundance of EGFR mutations was determined by receiver operating characteristic analysis in a training group and validated in a validation group.ResultsThe abundance of EGFR activating mutation by ARMS+ was significantly associated with objective response to EGFR TKIs. The abundance of 19DEL was significantly higher than that of L858R, with cutoff values for 19DEL and L858R of 4.9% and 9.5%, respectively. The median progression-free survival in the high group was significantly longer than that in the low group (19DEL, 15.0 versus 2.0 months [p < 0.001] and L858R, 12.3 versus 2.0 months [p < 0.001]) in the training set. Similar results were also observed in the validation set. Nine of 13 patients harboring T790M mutation achieved a partial response to EGFR TKIs. Most (seven of nine) were identified to have a low abundance of T790M mutation. The abundance of EGFR mutations appeared to be more significantly associated with the copy number of EGFR mutations from circulating tumor DNA in 19DEL group.ConclusionThe abundance of EGFR activating mutation by ARMS+ was significantly associated with objective response to EGFR TKIs. The abundance of EGFR^T790M mutation may have an adverse impact on progression-free survival rather than on objective response rate in patients with advanced EGFR-mutant NSCLC treated with EGFR TKIs.     

Osimertinib in Japanese patients with EGFR T790M mutation‐positive advanced non‐small‐cell lung cancer: AURA3 trial

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are the first‐line treatment for patients with EGFR mutant non‐small‐cell lung cancer (NSCLC). However, most patients become resistant to these drugs, so their disease progresses. Osimertinib, a third‐generation EGFR‐TKI that can inhibit the kinase even when the common resistance‐conferring Thr790Met (T790M) mutation is present, is a promising therapeutic option for patients whose disease has progressed after first‐line EGFR‐TKI treatment. AURA3 was a randomized (2:1), open‐label, phase III study comparing the efficacy of osimertinib (80 mg/d) with platinum‐based therapy plus pemetrexed (500 mg/m²) in 419 patients with advanced NSCLC with the EGFR T790M mutation in whom disease had progressed after first‐line EGFR‐TKI treatment. This subanalysis evaluated the safety and efficacy of osimertinib specifically in 63 Japanese patients enrolled in AURA3. The primary end‐point was progression‐free survival (PFS) based on investigator assessment. Improvement in PFS was clinically meaningful in the osimertinib group (n = 41) vs the platinum‐pemetrexed group (n = 22; hazard ratio 0.27; 95% confidence interval, 0.13‐0.56). The median PFS was 12.5 and 4.3 months in the osimertinib and platinum‐pemetrexed groups, respectively. Grade ≥3 adverse events determined to be related to treatment occurred in 5 patients (12.2%) treated with osimertinib and 12 patients (54.5%) treated with platinum‐pemetrexed. The safety and efficacy results in this subanalysis are consistent with the results of the overall AURA3 study, and support the use of osimertinib in Japanese patients with EGFR T790M mutation‐positive NSCLC whose disease has progressed following first‐line EGFR‐TKI treatment. (ClinicalTrials.gov trial registration no. NCT02151981.)     

A Novel Acquired Exon 20 EGFR M766Q Mutation in Lung Adenocarcinoma Mediates Osimertinib Resistance but is Sensitive to Neratinib and Poziotinib

IntroductionOsimertinib is an effective third-generation tyrosine kinase inhibitor (TKI) for EGFR-mutant lung cancers. However, treatment for patients with acquired resistance to osimertinib remains challenging. We characterized a novel EGFR mutation in exon 20 that was acquired while on osimertinib.MethodsA 79-year-old woman had disease progression during third-line treatment with osimertinib for an EGFR L858R/T790M–mutant lung cancer. Sequencing of circulating cell-free DNA showed EGFR L858R, an acquired novel EGFR M766Q mutation in exon 20, and no evidence of EGFR T790M. Homology modeling was performed to investigate the effects of M766Q on binding to osimertinib. L858R and L858R/M766Q mutations were retrovirally introduced into Ba/F3 and NIH/3T3 cells and evaluated for sensitivity to first-generation (erlotinib), second-generation (afatinib, neratinib, and poziotinib), and third-generation TKIs (osimertinib) by cell viability and colony-formation assays. EGFR-mediated signaling pathways were interrogated by western blotting.ResultsModeling suggested that EGFR M766Q could disrupt osimertinib binding. L858R/M766Q double-mutant cells were 12-fold more resistant to osimertinib, and more than 250-fold more resistant to erlotinib and afatinib, as compared to L858R-mutant cells. In contrast, double-mutant cells remained sensitive to neratinib and poziotinib at clinically relevant doses (concentration that inhibits 50%, 4.3 and 1.3 nM, respectively). This was corroborated by the effects of the TKIs on colony formation and EGFR signaling.ConclusionsAcquisition of EGFR M766Q exon 20 mutation is a novel mechanism of acquired resistance to osimertinib. EGFR-mutant lung cancers with an acquired EGFR M766Q mutation in the setting of osimertinib resistance may be sensitive to neratinib and poziotinib.     

Durvalumab for Stage III EGFR-Mutated NSCLC After Definitive Chemoradiotherapy

IntroductionIn 2018, durvalumab was approved by the U.S. Food and Drug Administration as consolidation immunotherapy for patients with stage III NSCLC after definitive chemoradiotherapy (CRT). However, whether durvalumab benefits patients with EGFR-mutated NSCLC remains unknown.MethodsWe conducted a multi-institutional retrospective analysis of patients with unresectable stage III EGFR-mutated NSCLC who completed concurrent CRT. Kaplan-Meier analyses evaluated progression-free survival (PFS) between patients who completed CRT with or without durvalumab.ResultsAmong 37 patients, 13 initiated durvalumab a median of 20 days after CRT completion. Two patients completed 12 months of treatment, with five patients discontinuing durvalumab owing to progression and five owing to immune-related adverse events (irAEs). Of 24 patients who completed CRT without durvalumab, 16 completed CRT alone and eight completed CRT with induction or consolidation EGFR tyrosine kinase inhibitors (TKIs). Median PFS was 10.3 months in patients who received CRT and durvalumab versus 6.9 months with CRT alone (log-rank p = 0.993). CRT and EGFR TKI was associated with a significantly longer median PFS (26.1 mo) compared with CRT and durvalumab or CRT alone (log-rank p = 0.023). Six patients treated with durvalumab initiated EGFR TKIs after recurrence, with one developing grade 4 pneumonitis on osimertinib.ConclusionsIn this study, patients with EGFR-mutated NSCLC did not benefit with consolidation durvalumab and experienced a high frequency of irAEs. Patients who initiate osimertinib after durvalumab may be susceptible to incident irAEs. Consolidation durvalumab should be approached with caution in this setting and concurrent CRT with induction or consolidation EGFR TKIs further investigated as definitive treatment.     

A Phase II Study of Osimertinib for Radiotherapy-Naive Central Nervous System Metastasis From NSCLC: Results for the T790M Cohort of the OCEAN Study (LOGIK1603/WJOG9116L)

ObjectivesOsimertinib has been reported to be effective against central nervous system (CNS) metastasis from activating EGFR mutation-positive NSCLC. Nevertheless, the true antitumor effects of osimertinib alone for CNS metastasis are unclear because the aforementioned studies included previously irradiated cases, in which tumor shrinkage can occur later owing to the effects of radiotherapy (RT). This study aimed to evaluate the efficacy of osimertinib against RT-naive CNS metastasis from sensitizing EGFR mutation-positive NSCLC.MethodsThe OCEAN study was a two-cohort trial, involving 66 patients (T790M cohort [n = 40] and first-line cohort [n = 26]) with RT-naive CNS metastasis from sensitizing EGFR mutation-positive NSCLC. The patients were treated once daily with 80 mg osimertinib. The primary end point was brain metastasis response rate (BMRR) according to the PAREXEL criteria. In this report, we present the results for the T790M cohort with analysis of drug concentrations and plasma circulating tumor DNA.ResultsThe median age of the patients was 69 years, and 30% of them were males. Eight patients (20%) were symptomatic, and most had multiple CNS metastases (78%). Among the eligible 39 patients, the BMRR (PAREXEL criteria), median brain metastasis-related progression-free survival (PFS), median overall survival, overall response rate, and median PFS were 66.7% (90% confidence interval: 54.3%–79.1%), 25.2 months, 19.8 months, 40.5%, and 7.1 months, respectively. The BMRR according to the Response Evaluation Criteria in Solid Tumors criteria was 70.0% (n = 20). The brain metastasis-related PFS of patients with EGFR exon 19 deletion was significantly longer than that of exon 21 L858R (median = 31.8 versus 8.3 mo; log-rank p = 0.032). The treatment-related pneumonitis was observed in four patients (10%). On or after day 22, the median trough blood and cerebrospinal fluid concentrations of osimertinib were 568 nM and 4.10 nM, respectively, and those of its metabolite AZ5104 were 68.0 nM and 0.260 nM, respectively. The median blood to cerebrospinal fluid penetration rates of osimertinib and AZ5104 were 0.79% and 0.53%, respectively. The blood trough concentration at day 22 was not correlated with the efficacy of osimertinib against CNS metastasis. Plasma T790M and C797S mutations were detected in 83% and 3% of the patients before treatment, 11% and 3% of the patients on day 22, and 39% and 22% of the patients at the detection of progressive disease, respectively.ConclusionsThis study evaluated the efficacy of osimertinib against RT-naive CNS metastasis from T790M-positive NSCLC. The primary end point was met, and the results revealed the efficacy of osimertinib in patients with CNS metastasis harboring EGFR T790M mutations especially for EGFR-sensitizing mutation of exon 19 deletion.     

Poor response to erlotinib in patients with tumors containing baseline EGFR T790M mutations found by routine clinical molecular testing

BackgroundEGFR T790M is the most common mutation associated with acquired resistance to EGFR tyrosine kinase inhibitors (TKIs). Baseline EGFR T790M mutations in EGFR TKI-naïve patients have been reported, but the frequency and their association with response to EGFR TKIs remain unclear.Patients and methodsThe frequency of baseline EGFR T790M as detected by routine molecular genotyping was determined by reviewing clinical results obtained at our institution from 2009 to 2013. We also collected outcome data for treatment with EGFR TKIs.ResultsTo define the incidence of EGFR T790M, we reviewed 2774 sequentially tested patients with lung cancer who underwent molecular testing using a mass spectrometry-based assay, and 11 (0.5%) had baseline EGFR T790M. Compiling results from several molecular techniques, we observed EGFR T790M in tumors from 20 patients who had not previously been treated with an EGFR TKI. In all cases, EGFR T790M occurred concurrently with another EGFR mutation, L858R (80%, 16/20), or exon 19 deletion (20%, 4/20). Two percent of all pre-treatment EGFR-mutant lung cancers harbored an EGFR T790M mutation. Thirteen patients received erlotinib monotherapy as treatment for metastatic disease. The response rate was 8% (1/13, 95% confidence interval 0%–35%). For the patients who received erlotinib, the median progression-free survival was 2 months and the median overall survival was 16 months.ConclusionsDe novo EGFR T790M mutations are rare (<1%) when identified by standard sensitivity methods. TKI therapy for patients with baseline EGFR T790M detected by standard molecular analysis has limited benefit.     

Primary resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in patients with non-small-cell lung cancer harboring TKI-sensitive EGFR mutations: an exploratory study

BackgroundThe mechanism of primary resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in EGFR-mutant non-small-cell lung cancer (NSCLC) has not been clearly understood.Patients and methodsEleven patients exhibiting primary resistance (disease progression <3 months) were identified among 197 consecutive NSCLC patients with TKI-sensitive EGFR mutations who received EGFR TKIs at Seoul National University Hospital. Treatment-naïve tumors were examined for concurrent genetic alterations using fluorescence in situ hybridization and targeted deep sequencing of cancer-related genes. Deletion polymorphism of Bcl-2-interacting mediator of cell death (BIM) gene was examined to validate its predictive role for TKI outcome.ResultsThe median progression-free survival (PFS) for patients receiving EGFR TKIs was 11.9 months, and the response rate 78.8%. Among the 11 patients exhibiting primary resistance, a de novo T790M mutation was identified in one patient, and two exhibited mesenchymal-epithelial transition amplification and anaplastic lymphoma kinase fusion. Targeted deep sequencing identified no recurrent, coexistent drivers of NSCLC. Survival analysis revealed that patients with recurrent disease after surgery had a longer PFS than those with initial stage IV disease. However, BIM deletion polymorphism, line of treatment, EGFR genotype, and smoking were not predictive of PFS for EGFR TKIs.ConclusionsWe identified coexistent genetic alterations of cancer-related genes that could explain primary resistance in a small proportion of patients. Our result suggests that the mechanism of primary resistance might be heterogeneous.     

Preclinical Modeling of Osimertinib for NSCLC With EGFR Exon 20 Insertion Mutations

IntroductionNSCLC with EGFR exon 20 insertion mutations is the third most common type of EGFR-mutant NSCLC and is resistant to EGFR tyrosine kinase inhibitors (TKIs). This study was conducted to evaluate the efficacies of first- to third-generation EGFR TKIs against NSCLC cells harboring EGFR exon 20 insertion mutations.MethodsWe developed seven EGFR exon 20 insertion-mutant Ba/F3 models and one patient-derived NSCLC (SNU-3173) of subtypes A763insFQEA, V769insASV, D770insSVD, D770insNPG, P772insPR, H773insH, H773insNPH, and H773insAH. Cell viability assays, immunoblotting, and N-ethyl-N-nitrosourea mutagenesis screenings were performed. EGFR exon 20 insertion–mutant structures and couplings with osimertinib, a third-generation EGFR TKI, were modeled and compared.ResultsEGFR exon 20 insertion–mutant NSCLC cells, excluding EGFR A763insFQEA, were resistant to first-generation EGFR TKIs (concentration that inhibits 50% [IC₅₀], 1.1 ± 0.067 to 5.4 ± 0.115 μM). Mutants were sensitive to second-generation EGFR TKIs (IC₅₀, 0.02 ± 0.0002 to 161.8 ± 18.7nM), except EGFR H773insH (IC₅₀, 46.3 ± 8.0 to 352.5 ± 22.7nM). The IC₅₀ ratios for mutant to wild-type cells were higher than those for third-generation EGFR TKIs. Third-generation EGFR TKI osimertinib was highly potent against EGFR exon 20 insertion–mutant cells (IC₅₀, 14.7-62.7 nM), including EGFR H773insH, and spared wild-type EGFR cells. N-ethyl-N-nitrosourea mutagenesis screening of EGFR exon 20 insertion–mutant Ba/F3 cells showed various second sites for EGFR mutations, mostly at exons 20 and 21, including E762K, P794S, and G796D. In addition, osimertinib-resistant cells were established by stepwise exposure to osimertinib and harbored EGFR E762K mutation.ConclusionsOsimertinib is active against EGFR exon 20 insertion–mutant NSCLC and flexibly binds within drug-binding pockets in preclinical models.     

<Emphasis Type="Italic">BIM</Emphasis> Deletion Polymorphism Confers Resistance to Osimertinib in <Emphasis Type="Italic">EGFR</Emphasis> T790M Lung Cancer: a Case Report and Literature Review

The third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) osimertinib (AZD9291) has shown significant clinical efficacy against the EGFR T790M mutation in non-small cell lung cancer (NSCLC) patients. However, resistance inevitably occurs, and the mechanisms leading to treatment failure need to be further investigated. The B-cell lymphoma 2 (BCL-2)-like 11 (BIM) deletion polymorphism, which occurs at a frequency of 21% in East Asians but is absent in African and European populations, has been associated with resistance to first-generation EGFR TKIs, such as gefitinib and erlotinib; and is a poor prognostic factor for NSCLC patients with EGFR mutations. Nevertheless, the significance of this BIM deletion polymorphism in the resistance to osimertinib has not been reported. Here, we show for the first time that a NSCLC patient harboring the EGFR L858R/T790M mutations, as well as the BIM deletion polymorphism, exhibited poor clinical outcomes with osimertinib treatment. This result suggests that the BIM deletion polymorphism might have prognostic value for determining NSCLC patient outcomes following osimertinib treatment.     

DualMET andERBB inhibition overcomes intratumor plasticity in osimertinib-resistant-advanced non-small-cell lung cancer (NSCLC)

BackgroundThird-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) such as osimertinib are the last line of targeted treatment of metastatic non-small-cell lung cancer (NSCLC)EGFR-mutant harboringT790M. Different mechanisms of acquired resistance to third-generation EGFR-TKIs have been proposed. It is therefore crucial to identify new and effective strategies to overcome successive acquired mechanisms of resistance.MethodsFor Amplicon-seq analysis, samples from the index patient (primary and metastasis lesions at different timepoints) as well as the patient-derived orthotopic xenograft tumors corresponding to the different treatment arms were used. All samples were formalin-fixed paraffin-embedded, selected and evaluated by a pathologist. For droplet digital PCR, 20 patients diagnosed with NSCLC at baseline or progression to different lines of TKI therapies were selected. Formalin-fixed paraffin-embedded blocks corresponding to either primary tumor or metastasis specimens were used for analysis. For single-cell analysis, orthotopically grown metastases were dissected from the brain of an athymic nu/nu mouse and cryopreserved at −80°C.ResultsIn a brain metastasis lesion from a NSCLC patient presenting anEGFR T790M mutation, we detectedMET gene amplification after prolonged treatment with osimertinib. Importantly, the combination of capmatinib (c-MET inhibitor) and afatinib (ErbB-1/2/4 inhibitor) completely suppressed tumor growth in mice orthotopically injected with cells derived from this brain metastasis. In those mice treated with capmatinib or afatinib as monotherapy, we observed the emergence ofKRAS G12C clones. Single-cell gene expression analyses also revealed intratumor heterogeneity, indicating the presence of aKRAS-driven subclone. We also detected low-frequentKRAS G12C alleles in patients treated with various EGFR-TKIs.ConclusionAcquired resistance to subsequent EGFR-TKI treatment lines inEGFR-mutant lung cancer patients may induce genetic plasticity. We assess the biological insights of tumor heterogeneity in an osimertinib-resistant tumor with acquiredMET-amplification and propose new treatment strategies in this situation.     

Uncommon EGFR Compound Mutations in Non-Small Cell Lung Cancer (NSCLC): A Systematic Review of Available Evidence

Compound epidermal growth factor receptor (EGFR) mutations represent a heterogeneous subgroup of non-small cell lung cancer (NSCLC) patients with uncommon EGFR mutations. We conducted a systematic review to investigate the available data on this patients’ subgroup. Overall, we found a high heterogeneity in the incidence of compound mutations (4–26% of total EGFR mutant cases), which is dependent on the different testing methods adopted and the specific mutations considered. In addition, the relative incidence of distinct compound subclasses identified is reported with extreme variability in different studies. Preclinical and clinical data, excluding de novo EGFR exon 20 p.T790M compound mutations, show good responses with EGFR tyrosine kinase inhibitors (TKIs) (combined common mutations: response rate (RR) ≥ 75% with either first- or second-generation TKIs; combined common plus uncommon: RR 40–80% and 100% with first-generation TKIs and afatinib, respectively; combined uncommon: RR 20–70%, ~80% and ~75% with first-generation TKIs, afatinib and osimertinib, respectively). Overall, data are consistent in supporting the use of EGFR TKIs in treating compound EGFR mutations, taking into account different sensitivity profile of accompanying EGFR mutations for selecting the most adequate EGFR TKI for individual patients.     

A Phase 1/2 Study of Lazertinib 240 mg in Patients With Advanced EGFR T790M-Positive NSCLC After Previous EGFR Tyrosine Kinase Inhibitors

IntroductionThis integrated analysis of a phase 1/2 study (NCT03046992) evaluated the efficacy and safety of lazertinib, a third-generation EGFR tyrosine kinase inhibitor (TKI), in patients with advanced EGFR T790M-positive NSCLC after previous EGFR TKI therapy.MethodsAdults with EGFR mutation-positive NSCLC that progressed after prior EGFR-directed TKIs received once daily oral lazertinib 240 mg continuously until disease progression. Prior TKIs to treat T790M-positive NSCLC were prohibited. Primary endpoints were safety and objective response rate (ORR). Secondary endpoints included progression-free survival, overall survival, and intracranial ORR.ResultsA total of 78 patients received lazertinib 240 mg at 17 centers in South Korea. Among patients with T790M-positive tumors at baseline (N = 76), one (1.3%) had a complete response and 41 (53.9%) had partial responses, giving an ORR of 55.3% (95% confidence interval [CI]: 44.1–66.4). Median progression-free survival was 11.1 months (95% CI: 5.5–16.4). Median overall survival was not reached (median follow-up = 22.0 mo). In patients with measurable intracranial lesions (n = 7), one (14.3%) had a complete intracranial response and five (71.4%) had partial responses, giving an intracranial ORR of 85.7% (95% CI: 59.8%–100.0%). The most common treatment-emergent adverse events were rash (37.2%), pruritus (34.6%), and paresthesia (33.3%); most were mild to moderate in severity. Serious drug-related adverse events occurred in three patients (gastritis, pneumonia, pneumonitis). The major mechanism of resistance was EGFR T790M loss.ConclusionsLazertinib 240 mg/d has a manageable safety profile with durable antitumor efficacy, including brain metastases, in patients with advanced T790M-positive NSCLC after previous EGFR TKI therapy.     

Continued EGFR Inhibition With Postprogression Chemotherapy: Where Do We Stand?

A growing body of evidence suggests that continuing EGFR inhibitors when switching to chemotherapy may not be the right choice for all patients. Nevertheless, a review of recent data about postprogression therapy for patients with EGFR-mutant lung cancer reveals some important caveats that must be considered when choosing the optimal treatment for patients who have progressed on their initial EGFR inhibitor.Patients with EGFR-mutant lung cancer are well known to benefit from EGFR-targeted therapies in the front-line setting, but once patients progress on their initial therapy, there is no standard approach or consensus about how best to proceed. Recently, the field has made great strides in understanding and treating acquired resistance caused specifically by T790M by using multiple new drugs in the later stages of clinical development. For patients who do not qualify for these newer drugs or who progress after trying them, standard chemotherapy remains the preferred treatment choice. However, the question of whether to maintain EGFR inhibition when switching to chemotherapy has been a subject of debate and active research.In this issue of The Oncologist, Halmos et al. [1] report the results of a randomized phase II study of pemetrexed or docetaxel chemotherapy with or without erlotinib among 46 patients who progressed on prior EGFR tyrosine kinase inhibitor (TKI) therapy. Although the population was heterogeneous (only ∼80% had a confirmed EGFR mutation and a significant proportion had received prior chemotherapy before going on erlotinib), the investigators found that the addition of EGFR TKI to chemotherapy did not improve progression-free survival (PFS). Moreover, the combination of chemotherapy with TKIs led to increased rates of treatment-related toxicities. Taken in the context of other recent studies of postprogression therapy for EGFR-mutant lung cancer, the study by Halmos et al. [1] adds to the growing body of evidence suggesting that continuing EGFR inhibitors when switching to chemotherapy may not be the right choice for all patients. Nevertheless, a review of recent data about postprogression therapy for patients with EGFR-mutant lung cancer reveals some important caveats that must be considered when choosing the optimal treatment for patients who have progressed on their initial EGFR inhibitor.Historically, the concept of maintaining EGFR suppression when switching to postprogression therapy was based on an understanding of the intrinsic heterogeneity of resistant cancers. Preclinical models demonstrate that the population of a resistant tumor can be heterogeneous, with some clones remaining sensitive to the original EGFR inhibitor [2, 3]. In the clinic, this heterogeneity is illustrated by patients who develop a disease “flare” with rapidly worsening disease-related symptoms when EGFR TKIs are stopped at the time of progression. Up to 25% of patients have been noted to develop such flares, and the rapid improvement of their symptoms on reinitiation of their original EGFR TKI suggested to many clinicians that maintaining continuous EGFR suppression could be of clinical benefit [4]. However, prospective, randomized studies aimed at identifying the optimal postprogression therapy were lacking and there was wide variability in clinical practice among the lung cancer community.In 2013, Goldberg et al. sought to examine the impact of continuing postprogression EGFR TKIs in combination with chemotherapy through a retrospective analysis of 78 EGFR-mutant non-small cell lung cancer (NSCLC) patients who progressed on erlotinib; of those, 34 received chemotherapy and erlotinib after progression and 44 received chemotherapy alone [5]. The study demonstrated a significant improvement in objective response rate (ORR) for those patients treated with the combination relative to those who received chemotherapy alone (ORR 41% vs. 18%; odds ratio: 0.20; p = .02.) Although there was no improvement in PFS or overall survival (OS) between the groups, the significant improvement in response rates suggested that maintaining EGFR suppression with postprogression chemotherapy might be of potential benefit and should be studied prospectively.Both the study of Halmos et al. [1] and the recently reported results of the larger IMPRESS trial [6] provide randomized, prospective data addressing the role of adding EGFR TKIs to postprogression chemotherapy among EGFR-mutant lung cancer patients. IMPRESS was a large Asian study that randomized 265 EGFR-mutant lung cancer patients to a standard chemotherapy regimen of cisplatin and pemetrexed with gefitinib versus placebo following progression on first-line gefitinib [6]. Much to the surprise of many clinicians, the results of the IMPRESS trial did not show a benefit with the addition of gefitinib to chemotherapy; there was no statistically significant difference in median PFS (5.4 months in both groups) or ORR (32% for gefitinib vs. 34% for placebo, p = .76) between the two groups. Although immature, early overall survival analyses suggest that chemotherapy with placebo may be superior to the addition of gefitinib. Although many questions remain and we eagerly await the results of follow-up survival analyses, the results of IMPRESS have already been practice changing for many clinicians, halting the common practice of keeping the EGFR TKI ongoing during chemotherapy.The study by Halmos et al. published in this issue of The Oncologist [1] further supports the results of the larger IMPRESS trial, demonstrating that the addition of an EGFR TKI to chemotherapy may not add benefit among patients who develop resistance to EGFR inhibitors. It is important to note that this small study was initiated in 2007, prior to widespread adoption of EGFR testing, and certain aspects of its design may not be applicable to today’s EGFR-mutant NSCLC patients. Patients were selected based on their previous response to EGFR inhibitors, but ultimately, only ∼80% had confirmed EGFR mutations identified. Moreover, a substantial proportion of the patients had been treated with chemotherapy prior to going on erlotinib, thus single-agent pemetrexed or docetaxel was used as the postprogression therapy. This practice may not reflect today’s EGFR-mutant NSCLC patients, who typically receive EGFR TKIs as their initial therapy and would be eligible for a platinum-pemetrexed chemotherapy regimen after progression (similar to the design of the IMPRESS trial.) Despite these caveats, the lack of improvement in ORR, PFS, or OS among those who continued TKI with chemotherapy is notable and in agreement with the results of the larger and more contemporary IMPRESS study. Although both the study by Halmos et al. and IMPRESS suggest that continuing EGFR TKIs when starting postprogression chemotherapy may not result in added benefit, several important issues remain to be considered by clinicians and patients faced with this decision in the clinic.First is the question of when to switch therapy. Both the trial by Halmos et al. and IMPRESS enrolled patients at the time of radiographic RECIST progression, but growing evidence shows that may not be the most appropriate clinical paradigm. Indeed, it is common for patients to continue on their initial EGFR TKI after the development of asymptomatic radiographic progression. This approach is supported by several recent studies. Lo et al. retrospectively analyzed the records of 42 patients treated with first-line erlotinib and determined that most patients were able to continue erlotinib after RECIST progression; the median time to a change in systemic therapy after RECIST progression was 3.2 months, although 21% of patients could delay therapy change for a year or more [7]. In particular, certain variables were identified as predictors of longer time to treatment change. These included longer time to progression on initial erlotinib, progression occurring at existing disease sites without new extrathoracic metastatic locations, and a slower rate of linear radiographic tumor growth. Similarly, the recent prospective ASPIRATION trial also demonstrated that patients could continue to benefit from erlotinib after RECIST progression, with a median postprogression duration of treatment of 3.1 months [8]. Similar to the retrospective analysis by Lo et al., ASPIRATION showed that patients who responded well to first-line erlotinib were most likely to be able to continue erlotinib after progression. Taken together, the results of these studies suggest that many patients may benefit from the continuation of first-line EGFR inhibitors even following the development of progressive disease by RECIST criteria. Although there are limited prospective data to identify the optimal time to switch therapy, a common clinical paradigm is to continue the initial EGFR TKI alone until patients begin to develop clinical signs of progression or until there is concern for complications based on the size, radiographic appearance, or location of growing lesions.Second, although the resistance mechanisms to initial EGFR therapy were not reported for the patients included in IMPRESS or in the trial by Halmos et al., it is essential to consider the mechanism of acquired resistance to front-line therapy when selecting postprogression therapy. In particular, the 50%–60% of patients who harbor the T790M resistance mutation following progression on front-line EGFR TKIs are likely to benefit from novel, T790M-specific EGFR inhibitors such rociletinib (CO-1686), osimertinib (AZD9291), and others [9–13]. Although these agents are currently available only through clinical trials, they have shown impressive clinical activity for T790M-positive patients, and U.S. Food and Drug Administration approvals of at least two of these are expected in the coming months. Consequently, for patients with T790M-positive progression on erlotinib, gefitinib, or afatinib, the standard paradigm will soon include switching to a T790M-specific EGFR inhibitor rather than second-line chemotherapy. Indeed, the considerations surrounding optimal second-line chemotherapy regimens and whether to continue a first-generation EGFR inhibitor will be most relevant to those patients whose tumors are T790 wild type and for which no other targetable resistance mechanisms are identified.Recently, a plasma biomarker analysis of the IMPRESS study data presented at the International Association for the Study of Lung Cancer 2015 World Conference on Lung Cancer addressed the question of whether T790M status affected the benefit of continuing a TKI with chemotherapy. The investigators found that patients without detectable T790M in the plasma had a trend toward improvement in PFS when treated with chemotherapy plus gefitinib (6.7 months) relative to chemotherapy plus placebo (5.4 months; hazard ratio: 0.67; p = .07) [14]. Because the T790M-negative patients are currently those most likely to go on to chemotherapy (i.e., less likely to receive a third-generation T790M-specific EGFR TKI), the results of this biomarker analysis are paramount to our understanding of the overall IMPRESS data and will need to be validated in larger studies looking specifically at the T790M-negative patient population.Ultimately, the decision about optimal postprogression therapy for EGFR-mutant lung cancer patients is a complex one that must be tailored for each patient. In general, growing evidence shows that the development of RECIST progression may not immediately necessitate a switch in therapy and that some patients may be able to continue on their initial EGFR inhibitor for many months before developing a clinical need for change in treatment. Whenever possible, repeated molecular testing to identify resistance mechanisms (through noninvasive plasma circulating tumor DNA analysis or repeat tissue biopsy) should be obtained to guide further therapy. For patients with detectable T790M, third-generation T790M-specific EGFR inhibitors are becoming a standard of care and soon will be entering widespread use. For patients who are T790M-negative, clinical trials should be considered when available. Indeed, third-generation EGFR inhibitors may also have some activity among T790M-negative patients, and further investigation of their role in the treatment of this patient population is eagerly awaited [15].For now, second-line chemotherapy remains the standard of care for all patients, particularly those without T790M or other targetable resistance mechanisms. Although the current data including the overall results of the IMPRESS trial and the work by Halmos et al. published in this issue of The Oncologist do not support the continuation of an EGFR TKI when switching to second-line chemotherapy in general, the recent biomarker analysis of the IMPRESS study suggests that T790M-negative patients may indeed benefit from continuing EGFR inhibition. In addition, patients who have had previous signs or symptoms of disease flare when holding EGFR inhibitors may be at increased risk of developing another flare and also may benefit from continuing EGFR suppression with chemotherapy. Going forward, further prospective studies incorporating current clinical standards such as allowing postprogression EGFR TKI monotherapy and focusing on T790M-negative patients will be needed to determine the optimal treatment regimen for EGFR-mutant patients progressing on front-line therapies.     

Audit of Molecular Mechanisms of Primary and Secondary Resistance to Various Generations of Tyrosine Kinase Inhibitors in Known Epidermal Growth Factor Receptor-Mutant Non-small Cell Lung Cancer Patients in a Tertiary Centre

AimsPresently, three generations of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are approved against oncogene addicted EGFR-mutant non-small cell lung cancer (NSCLC). Patients with actionable EGFR mutations invariably develop resistance. This resistance can be intrinsic (primary) or acquired (secondary).Materials and methodsThis was a retrospective study carried out between January 2016 and April 2021 analysing 486 samples of NSCLC for primary and secondary resistance to first- (erlotinib, gefitinb), second- (afatinib) and/or third-generation (osimertinib) TKIs in EGFR-mutant NSCLCs by next generation sequencing (NGS). Tissue NGS was carried out using the Thermofischer Ion Torrent? Oncomine? Focus 52 gene assay; liquid biopsy NGS was carried out using the Oncomine Lung Cell-Free Total Nucleic Acid assay. All cases were previously tested for a single EGFR gene with the Therascreen® EGFR RGQ PCR kit.ResultsThe results were divided into four groups: (i) group 1: primary resistance to first- and/or second-generation TKIs. This group, with 21 cases, showed EGFR exon 20 insertions, dual, complex mutations and variant of unknown significance, de novo MET gene amplification besides other mutations. (ii) Group 2: primary resistance to third-generation TKIs. This group showed two cases, with one showing dual EGFR mutation (L858R and E709A) and EGFR gene amplification. (iii) Group 3: secondary resistance to first- and second-generation TKIs. This group had 27 cases, which were previously reported negative for EGFR T790M by single gene testing. Significant findings were MET gene amplification in four cases, with one also showing MET exon 14 skipping mutation. Three cases showed small cell change and one showed loss of primary mutation. (iv) Group 4: secondary resistance to third-generation TKIs. The latter group was further subgrouped into group 4A: secondary resistance to osimertinib (third-generation TKI) when offered as second-line therapy after first- and second-generation TKIs on detection of T790M mutation. This group had 15 cases. EGFR T790M mutation was lost in 10 (10/15; 67%) cases and was retained in five cases. Patients with T790M loss experienced early resistance (6.9 months versus 12.6 months mean, P = 0.0024) compared with cases that retained T790M. Two cases gained MET amplification as the resistance mechanisms. Other mutations that were found when EGFR T790M was lost were in FGFR3, KRAS, PIK3CA, CTNNB1, BRAF genes. One case had EML4-ALK translocation. Two cases showed driver EGFR deletion 19, retained T790M and C797S mutation in Cis form. Group 4B: secondary resistance to osimertinib (when given as first-line therapy) in EGFR-mutant NSCLC. This group had three cases. The duration of osimertinib treatment ranged from 11 to 17 months. Two patients showed additional C797S mutation along with primary EGFR mutation.ConclusionThis study shows the wide spectrum of primary and secondary EGFR resistance mechanisms to first, second and third generation of TKIs and helps us to identify newer therapeutic targets that could carry forward the initial advantage offered by EGFR TKIs.     

EGFR exon 20 Insertion NSCLC and Response to Platinum-Based Chemotherapy

IntroductionIn classical EGFR mutant non-small-cell lung cancer (NSCLC), EGFR tyrosine kinase inhibitor (TKI) therapy yields better outcomes than platinum-based chemotherapy. However, EGFR exon 20 insertion (ex20ins) NSCLC is relatively resistant to currently available EGFR TKIs. Though platinum-based chemotherapy is the frontline standard of care for EGFR ex20ins NSCLC, its efficacy is not fully described.Study DesignA retrospective, single-center, case seriesMethodsPatients were identified through an electronic research database at a single institution and included if they had advanced EGFR ex20ins NSCLC, received platinum-based chemotherapy for metastatic disease, and had scans evaluable for response. Each patient's demographics, tumor characteristics, and clinical course were recorded. Treatment response was evaluated using RECIST v1.1 criteria, and the PFS was calculated by the Kaplan-Meier method.ResultsAmong 27 patients identified with EGFR ex20ins NSCLC at our institution, 18 (67%) received platinum-based chemotherapy for metastatic disease and had scans evaluable for response. These patients received platinum-based chemotherapy in the first-line (N = 17, 94%) and second-line settings (N = 1, 6%). The objective response rate (ORR) to platinum-based chemotherapy was 39% (7 of 18 patients; 95% confidence interval [CI] 16-61). The median PFS with platinum-based chemotherapy was 7.1 months (95% CI, 6.3 -13.7), and the median overall survival was 3.2 years (95% CI, 1.92 – NR).ConclusionsThe efficacy of platinum-based chemotherapy in EGFR ex20ins NSCLC is similar to that expected for TKI sensitive EGFR mutant NSCLC. Novel agents designed to specifically target ex20ins mutant EGFR should additionally improve outcomes.     

Tumor immune microenvironment and nivolumab efficacy in EGFR mutation-positive non-small-cell lung cancer based on T790M status after disease progression during EGFR-TKI treatment

BackgroundThe efficacy of programmed death-1 blockade in epidermal growth factor receptor gene (EGFR) mutation-positive non-small-cell lung cancer (NSCLC) patients with different mechanisms of acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) is unknown. We retrospectively evaluated nivolumab efficacy and immune-related factors in such patients according to their status for the T790M resistance mutation of EGFR.Patients and methodsWe identified 25 patients with EGFR mutation-positive NSCLC who were treated with nivolumab after disease progression during EGFR-TKI treatment (cohort A). Programmed death-ligand 1 (PD-L1) expression and tumor-infiltrating lymphocyte (TIL) density in tumor specimens obtained after acquisition of EGFR-TKI resistance were determined by immunohistochemistry. Whole-exome sequencing of tumor DNA was carried out to identify gene alterations. The relation of T790M status to PD-L1 expression or TIL density was also examined in an independent cohort of 60 patients (cohort B).ResultsIn cohort A, median progression-free survival (PFS) was 2.1 and 1.3 months for T790M-negative and T790M-positive patients, respectively (P = 0.099; hazard ratio of 0.48 with a 95% confidence interval of 0.20–1.24). Median PFS was 2.1 and 1.3 months for patients with a PD-L1 expression level of ≥1% or <1%, respectively (P = 0.084; hazard ratio of 0.37, 95% confidence interval of 0.10–1.21). PFS tended to increase as the PD-L1 expression level increased with cutoff values of ≥10% and ≥50%. The proportion of tumors with a PD-L1 level of ≥10% or ≥50% was higher among T790M-negative patients than among T790M-positive patients of both cohorts A and B. Nivolumab responders had a significantly higher CD8⁺ TIL density and nonsynonymous mutation burden.ConclusionT790M-negative patients with EGFR mutation-positive NSCLC are more likely to benefit from nivolumab after EGFR-TKI treatment, possibly as a result of a higher PD-L1 expression level, than are T790M-positive patients.     

Genotyping of Cerebrospinal Fluid Associated With Osimertinib Response and Resistance for Leptomeningeal Metastases in EGFR-Mutated NSCLC

IntroductionPatients with NSCLC with leptomeningeal metastases (LM) presented dismal prognosis. Cerebrospinal fluid (CSF) is suggested as a medium of liquid biopsy of LM. However, the clinical implications of CSF genotyping on treatment outcomes remained elusive.MethodsPatients with EGFR-mutated advanced NSCLC with LM were included: cohort 1, patients with LM who were treated with osimertinib with CSF and plasma genotyping performed before the first dosing of osimertinib (baseline, n = 45); cohort 2, CSF genotyping on progression on osimertinib and development of LM (the progression event on osimertinib is the diagnosis of LM, n = 35). Circulating tumor DNA in CSF underwent next-generation sequencing.ResultsSensitivity of CSF genotyping for EGFR-sensitizing mutations was 93.3% (42 of 45) and 97.1% (34 of 35) in cohorts 1 and 2, respectively. In cohort 1, patients with EGFR exon 19 deletion had higher median intracranial progression free survival (iPFS) than those with EGFR exon 21 L858R mutation (11.9 versus 2.8 mo; p = 0.02). Median iPFS was significantly longer in patients with T790M-positive CSF genotyping (15.6 mo) than T790M-negative CSF (7.0 mo, p = 0.04). Concurrent CDK4 (2.8 versus 11.6 mo, p = 0.002) and CDKN2A (2.5 versus 9.6 mo, p = 0.04) mutation with EGFR-sensitizing mutations indicated lower median iPFS. Patients with T790M-negative CSF, EGFR exon 21 L858R mutation, concurrent FGF3 alteration, and over first-line osimertinib had shortened iPFS. In cohort 2, possible EGFR-related and EGFR-independent resistance mechanisms were found including C797S mutation, MET dysregulation, and TP53 plus RB1 co-occurrence. Patients with loss of T790M in CSF had a shorter median iPFS (7.4 mo) compared with those with reserved T790M (13.6 mo, p = 0.01).ConclusionsGenotyping of CSF indicated heterogeneous response to osimertinib and revealed the genetic characteristic of LM on osimertinib failure in patients with EGFR-mutated NSCLC diagnosed with LM.     

CD73 Inhibitor Oleclumab Plus Osimertinib in Previously Treated Patients With Advanced T790M-Negative EGFR-Mutated NSCLC: A Brief Report

IntroductionCD73 is overexpressed in EGFR-mutated NSCLC and may promote immune evasion, suggesting potential for combining CD73 blockers with EGFR tyrosine kinase inhibitors (TKIs). This phase 1b-2 study (NCT03381274) evaluated the anti-CD73 antibody oleclumab plus the third-generation EGFR TKI osimertinib in advanced EGFR-mutated NSCLC.MethodsPatients had tissue T790M-negative NSCLC with TKI-sensitive EGFR mutations after progression on a first- or second-generation EGFR TKI and were osimertinib naive. They received osimertinib 80 mg orally once daily plus oleclumab 1500 mg (dose level 1 [DL1]) or 3000 mg (DL2) intravenously every 2 weeks. Primary end points included safety and objective response rate by Response Evaluation Criteria in Solid Tumors version 1.1.ResultsBy July 9, 2021, five patients received DL1 and 21 received DL2. Of these patients, 60.0% and 85.7% had any-grade treatment-related adverse events (TRAEs) and 20.0% and 14.3% had grade 3 TRAEs, respectively. No dose-limiting toxicities, serious TRAEs, or deaths occurred. Four patients were T790M positive on retrospective circulating tumor DNA (ctDNA) testing; three had objective partial responses. In patients who were T790M negative in tumor and ctDNA, objective response rate was 25.0% at DL1 and 11.8% at DL2 (all partial responses); response durations at DL2 were 14.8 and 16.6 months. In patients receiving DL2, excluding those who were T790M positive by ctDNA, median progression-free survival was 7.4 months, and median overall survival was 24.8 months. DL2 was the recommended phase 2 dose.ConclusionsOleclumab plus osimertinib was found to have moderate activity with acceptable tolerability in previously treated patients with advanced EGFR-mutated NSCLC.