Response to Subsequent Docetaxel in a Patient Cohort With Metastatic Castration-Resistant Prostate Cancer After Abiraterone Acetate Treatment

Introduction/BackgroundDocetaxel or AA are therapeutic options for mCRPC. We retrospectively analyzed clinical outcomes with subsequent docetaxel in patients with mCRPC after disease progression (DP) with AA to evaluate cross resistance between these therapies.Patients and MethodsPatients with chemotherapy-naive mCRPC who were treated with AA in previously reported phase I to III trials, who had DP, and were subsequently treated (not on study) with docetaxel, were included. Acquired AA resistance was defined as: PSA decline > 50% from baseline or radiographically stable disease for ≥ 8 months, with subsequent DP. All other patients were defined as having primary AA resistance. Efficacy outcomes after docetaxel therapy were analyzed.ResultsWe identified 23 patients who were treated with docetaxel after DP with AA, including 14 (61%) with acquired and 9 (39%) with primary AA resistance. Median duration between discontinuation of AA and docetaxel initiation was 2.7 months (range, 0.2-14.7 months). Subsequent docetaxel therapy led to ≥ 30% PSA decline in 15 patients (65%) and ≥ 50% PSA decline in 11 patients (48%). Median OS from date of first docetaxel dose was 12.4 months (95% confidence interval, 8.2-19.6). Patients with previous primary versus acquired AA resistance had similar outcomes with subsequent docetaxel therapy.ConclusionIn this retrospective analysis, the type of AA resistance did not appear to affect outcomes with subsequent docetaxel. The PSA response rates observed suggest a lack of cross-resistance between docetaxel and AA, but prospective studies are needed to evaluate for potential cross-resistance and optimize sequences of therapy in patients with mCRPC.     

Randomized phase II trial of docetaxel plus prednisone in combination with placebo or AT-101, an oral small molecule Bcl-2 family antagonist, as first-line therapy for metastatic castration-resistant prostate cancer

BackgroundAT-101 (A), a small molecule oral inhibitor of the Bcl-2 family, has activity alone and in combination with docetaxel (Taxotere) and prednisone (DP) in metastatic castration-resistant prostate cancer (mCRPC). A randomized, double-blind, placebo-controlled phase II trial compared DP combined with either AT-101 (A) or placebo in chemonaive mCRPC.Patients and methodsMen with progressive mCRPC despite androgen deprivation were eligible and randomized 1 : 1. Patients received docetaxel (75 mg/m² day 1) and prednisone 5 mg orally twice daily every 21 days with either AT-101 (40 mg) or placebo twice daily orally on days 1–3. The primary end point was overall survival (OS).ResultsTwo hundred and twenty-one patients were randomly assigned. Median OS for AT-101 plus docetaxel–prednisone (ADP) and placebo–DP was 18.1 versus 17.8 months [hazard ratio (HR) 1.07, 95% confidence interval 0.72–1.55, P = 0.63]. Secondary end points were also not statistically different. Grade 3/4 toxic effects for ADP versus placebo–DP were cardiac events (5% versus 2%), lymphopenia (23% versus 16%), neutropenia (47% versus 40%), ileus (2% versus 0%) and pulmonary embolism (6% versus 2%). In a subgroup of high-risk mCRPC (n = 34), outcomes appeared to favor ADP (median OS 19 versus 14 months).ConclusionsAT-101 was tolerable but did not extend OS when combined with DP in mCRPC; a potential benefit was observed in high-risk patients.     

Phase I Trial of the Combination of Docetaxel,Prednisone, and Pasireotide in Metastatic Castrate-Resistant Prostate Cancer

Background

Pasireotide (SOM230; Novartis Inc, Basel, Switzerland) is a multitargeted somatostatin receptor analogue likely to treat the neuroendocrine, and docetaxel resistant components within metastatic castrate-resistant prostate cancer (mCRPC). This phase I trial tested the combination of pasireotide, docetaxel, and prednisone in pretreated mCRPC.

Phase I/II trial of cabazitaxel plus abiraterone in patients with metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel and abiraterone

BackgroundAbiraterone and cabazitaxel improve survival in patients with metastatic castration-resistant prostate cancer (mCRPC). We conducted an open-label phase I/II trial of cabazitaxel plus abiraterone to assess the antitumor activity and tolerability in patients with progressive mCRPC after docetaxel (phase I), and after docetaxel and abiraterone (phase II) (NCT01511536).Patients and methodsThe primary objectives were to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of cabazitaxel plus abiraterone (phase I), and the prostate-specific antigen (PSA) response defined as a ≥ 50% decrease confirmed ≥3 weeks later with this combination (phase II).ResultsTen patients were enrolled in the phase I component; nine were evaluable. No DLTs were identified. The MTD was established as the approved doses for both drugs (cabazitaxel 25 mg/m² every 3 weeks and abiraterone 1000 mg once daily). Daily abiraterone treatment did not impact on cabazitaxel clearance. Twenty-seven patients received cabazitaxel plus abiraterone plus prednisone (5 mg twice daily) in phase II. The median number of cycles administered (cabazitaxel) was seven (range: 1–28). Grade 3–4 treatment-emergent adverse events included asthenia (in 5 patients; 14%), neutropenia (in 5 patients; 14%) and diarrhea (in 3 patients; 8%). Nine patients (24%) required dose reductions of cabazitaxel. Of 26 evaluable patients, 12 achieved a PSA response [46%; 95% confidence interval (CI): 26.6–66.6%]. Median PSA-progression-free survival was 6.9 months (95% CI: 4.1–10.3 months). Of 14 patients with measurable disease at baseline, 3 (21%) achieved a partial response per response evaluation criteria in solid tumors.ConclusionsThe combination of cabazitaxel and abiraterone has a manageable safety profile and shows antitumor activity in patients previously treated with docetaxel and abiraterone.     

Safety and Efficacy of Maintenance Therapy With a Nonspecific Cytochrome P17 Inhibitor (CYP17i) After Response/Stabilization to Docetaxel in Metastatic Castration-Resistant Prostate Cancer

BackgroundFrontline treatment of metastatic castration-resistant prostate cancer (mCRPC) consists of docetaxel-based chemotherapy. The median time to progression (TTP) from chemotherapy initiation is 6 to 8 months. Ketoconazole, a nonspecific cytochrome P17 inhibitor (CYP17i), blocks adrenal androgen synthesis. Low-dose ketoconazole (LDK), (200 mg three times daily [t.d.s]) has shown activity in mCRPC after progression to androgen deprivation. The role of a CYP17i after docetaxel treatment in the maintenance setting has been unexplored.MethodsWe identified 38 patients with mCRPC who showed progression to luteinizing hormone releasing–hormone agonists (LHRHa) and who were treated with a median of 7 cycles of frontline three-weekly docetaxel (75 mg/m²) plus prednisone (10 mg/d) and LHRHa. Medical charts of 20 patients who showed no progression to docetaxel were reviewed. After the last docetaxel cycle, 10 patients received LDK maintenance treatment plus prednisone (10 mg/d) and LHRHa, whereas 10 patients received LHRHa alone. TTP was the primary endpoint.ResultsAfter a follow-up of 27 months, disease in all patients receiving LHRHa alone progressed, whereas 8/10 patients progressed to maintenance therapy. Median TTP from docetaxel initiation was 11.5 months (95% confidence interval [CI], 6.3-16.6) for maintenance therapy and 9.2 months (95% CI, 8.5-9.9) for LHRHa alone (P = .047). The maintenance treatment was well tolerated. Only 1 patient experienced a grade 4 adverse event due to a nonsymptomatic pulmonary embolism.ConclusionThis is the first study evaluating a CYP17i for maintenance therapy after docetaxel therapy. We showed a 2-month significant benefit in TTP for patients with mCRPC treated with LDK maintenance therapy after docetaxel, with a favorable toxicity profile. A large prospective randomized study using a CYP17i is warranted.     

Weekly cabazitaxel plus prednisone is effective and less toxic for ‘unfit’ metastatic castration-resistant prostate cancer: Phase II Spanish Oncology Genitourinary Group (SOGUG) trial

AimCabazitaxel (CBZ), a novel tubulin-binding taxane, improves overall survival in metastatic castration-resistant prostate cancer (mCRPC) that progresses during or after docetaxel treatment. We have designed a phase II study to evaluate the efficacy and safety of CBZ as a weekly schedule for ‘unfit’ mCRPC patients after docetaxel failure.MethodsIn this single arm phase II study. CBZ was weekly administered in 1-hour infusion on days 1, 8, 15 and 22, every 5 weeks at 10 mg/m² to eligible ‘unfit’ patients; oral prednisone (5 mg) was administered twice a day. Circulating tumour cells (CTCs) were also collected. New treatment scheme was considered effective if at least 65% of patients met a clinical benefit criteria based on prostate-specific antigen (PSA)-progression-free survival (PFS) values at week 12.ResultsSeventy patients (median age: 73.9 years) were enrolled; overall, 71.4% had an Eastern Cooperative Oncology Group Performance Status (ECOG-PS) of 2; and 84%, 16% and 11% had bone, liver and lung metastases, respectively. Objective partial response or stable disease was achieved in 61% of patients, while PSA responses of ≥50% and ≥80% were observed in 34.8% and 10.6%, respectively. The median PSA-PFS was 4.8 months; and 68.6% of patients had no progression at week 12. The most frequent grade 3/4 toxicities were neutropenia (2.8%), leukopenia (5.7%) and thrombocytopaenia (9%); no cases of febrile neutropenia were reported. Early CTC response was significantly correlated with PSA-PFS.ConclusionsCBZ/prednisone administered weekly to ‘unfit’ mCRPC patients appears to be as effective as classical standard 3-week scheme (TROPIC study) but with significantly lower toxicities and better tolerance. Early CTC response appears to be valuable as an early end-point of therapeutic efficacy.     

Translating clinical trials to clinical practice: outcomes of men with metastatic castration resistant prostate cancer treated with docetaxel and prednisone in and out of clinical trials

BackgroundMultiple factors can influence outcomes of patients receiving identical interventions in clinical trials and in routine practice. Here, we compare outcomes of men with metastatic castrate-resistant prostate cancer (mCRPC) treated with docetaxel and prednisone in routine practice and in clinical trials.Patients and methodsWe reviewed patients with mCRPC treated with docetaxel at Princess Margaret Cancer Centre. Primary outcomes were overall survival and PSA response rate. Secondary outcomes were reasons for discontinuation and febrile neutropenia. Outcomes were compared for men treated in routine practice and in clinical trials, and with data from the TAX 327 study.ResultsFrom 2001 to 2011, 438 men were treated, of whom 357 received 3-weekly docetaxel as first-line chemotherapy: 314 in routine practice and 43 in clinical trials. Trial patients were younger and had better performance status. Median survival was 13.6 months [95% confidence interval (95% CI) 12.1–15.1 months] in routine practice and 20.4 months (95% CI 17.4–23.4 months, P = 0.007) within clinical trials, compared with 19.3 months (95% CI 17.6–21.3 months, P < 0.001) in the TAX 327 study. PSA response rates were 45%, 54%, and 53%, respectively (P = NS). Reasons for treatment discontinuation were similar although trial patients received more cycles (median: 6 versus 8 versus 9.5, P < 0.001). Rates of febrile neutropenia were 9.6, 0, and 3% (P < 0.001) while rates of death within 30 days of last dose were 4%, 0%, and 3%, respectively (P = NS).ConclusionsSurvival of patients with mCRPC treated with docetaxel in routine practice is shorter than for men included in trials and is associated with more toxicity.     

Clinical activity of abiraterone acetate in patients with metastatic castration-resistant prostate cancer progressing after enzalutamide

BackgroundAbiraterone acetate and enzalutamide both improve outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC). Optimal sequencing for these agents and whether cross-resistance occurs is unknown.MethodsMulticentre review of patients with mCRPC treated with abiraterone acetate and prednisone after progressing on enzalutamide. Primary objective was to determine abiraterone acetate response.ResultsThirty patients identified from four North American centres. At abiraterone initiation, median age was 70 years (56–84 years); 70% had ECOG performance status of 0–1; all had prior docetaxel. Median prior enzalutamide treatment duration was 41 weeks (6–95 weeks), with 70% (21 of 30) having a ≥30% prostate-specific antigen (PSA) decline. Median abiraterone acetate treatment duration was 13 weeks (1–52). No objective radiographic responses were observed. Median abiraterone time to progression (PSA, objective or symptomatic) was 15.4 weeks [95% confidence interval (CI) 10.7–20.2]. Median overall survival was 50.1 weeks (95% CI 28.3–72.0). Three patients had a ≥30% PSA decline with abiraterone. Two of these patients had PSA progression as best response with prior enzalutamide.ConclusionsIn this study of patients progressing after enzalutamide, treatment with abiraterone was associated with a modest response rate and brief duration of effect. Primary progression on enzalutamide may not preclude a response to abiraterone.     

Activity of Cabazitaxel After Docetaxel and Abiraterone Acetate Therapy in Patients With Castration-Resistant Prostate Cancer

BackgroundCabazitaxel and AA have been approved by the US Food and Drug Administration for use after docetaxel in mCRPC. Recently, CAB appeared to be active when given after AA. AA is capable of inducing AR splice variants that confer ligand-independent AR transactivation. Because microtubule-targeting agents impair AR nuclear transport and activity, we raised concerns about CAB efficacy after AA failure in mCRPC.Patients and MethodsOne hundred thirty mCRPC patients received AA after docetaxel treatment in compassionate programs. Of them, 24 (18.4%) subsequently received CAB. We retrospectively reviewed their data using conventional methods.ResultsTwenty-four patients received a median of 4 (range, 1-13) CAB cycles. Nineteen (79.1%) of them received primary prophylaxis with growth factors. Median patient characteristics were: age 65 (range, 57-85) years; Gleason score: 8 (range, 6-10); and PSA: 128.1 (range, 0.01-1700) ng/mL. A PSA response (≥ 50% decrease from baseline) occurred in 6 (31.5%) of 19 evaluable patients (95% confidence interval [CI], 11.8-54.2%). CAB therapy obtained a partial response in 2 of the 13 (15.3%) evaluable patients (95% CI, 2.9-45.4%). Median survival from initiation of CAB was 8.2 (95% CI, 3.34-13.05) months, from AA 16.1 (95% CI, 11.56-20.64) and from docetaxel 32.0 (95% CI, 11.56-39.69).ConclusionA limited number of patients with mCRPC received CAB after docetaxel and AA treatment. In this selected population, CAB was active.     

Phase I study of sorafenib in combination with docetaxel and prednisone in chemo-na?ve patients with metastatic castration-resistant prostate cancer

Purpose

We performed a dose-escalation study to investigate the safety of sorafenib in combination with docetaxel and prednisone in chemo-na?ve patients with metastatic castration-resistant prostate cancer (mCRPC).

Methods

Six patients were included per dose level. Following docetaxel infusion on day 1 (75?mg/m²/q3?weeks), sorafenib was administered at 200?mg BID on days 2?C19 (dose level 1), at 200?mg BID on days 1?C21 (dose level 2), at 400?mg BID on days 2?C19 (dose level 3), at 400?mg BID on days 1?C21 (dose level 4). Maximal tolerated dose (MTD) was exceeded if ??2 patients experienced dose-limiting toxicities (DLT) during cycle 1. The recommended phase 2 dose for sorafenib was defined as one dose level below MTD. If MTD was not reached, the highest feasible dose would be selected to treat an expanded cohort to confirm safety.

Results

Two DLTs were observed during sorafenib dose-escalation consisting of grade 4 febrile neutropenia (dose level 2) and grade 3 hand-foot syndrome (HFS) (dose level 3). Our pharmacokinetic results showed an increased exposure to docetaxel across all dose levels during sorafenib comedication. The main grade ??3 toxicities were neutropenia (35?%), HFS (27?%), and febrile neutropenia (19?%). The prostate-specific antigen (PSA) response rate was 74?%. Median overall survival was 25.2?months.

Conclusion

Three-weekly docetaxel and prednisone could be combined with sorafenib at 400?mg BID on days 1?C21 without reaching MTD. However, we observed a pharmacokinetic interaction between sorafenib and docetaxel, associated with significant toxicities, raising concerns about the safety of this combination in mCRPC.     

Phase II trial of the PI3 kinase inhibitor buparlisib (BKM-120) with or without enzalutamide in men with metastatic castration resistant prostate cancer

BackgroundPhosphatidylinositol-3-kinase (PI3K) and androgen receptor pathway activation is common in metastatic castration resistant prostate cancer (mCRPC). Buparlisib is an oral, pan-class I PI3 kinase inhibitor.MethodsThis was a multisite single arm phase II trial of buparlisib 100 mg ± enzalutamide daily in men with mCRPC whose disease progressed on or who were not candidates for docetaxel. The primary end-point was the rate of radiographic/clinical progression-free survival (PFS) at 6 months.ResultsThirty men were accrued: 67% post-docetaxel; median prostate specific antigen (PSA) was 70 ng/dl, 83% had ≥4 prior therapies for mCRPC; 43% received concurrent enzalutamide. The final 6 month PFS rate was estimated to be 10% (95% confidence interval 2.5–23.6%). Median PFS was 1.9 months and was 3.5 months with concurrent enzalutamide. Median overall survival was 10.6 months. Concurrent enzalutamide led to a five-fold reduction in buparlisib concentrations. PSA declines were observed in 23%; no patients achieved a ≥50% decline, and no radiographic responses were observed. Severe adverse events occurred in four men including respiratory infection and multi-organ failure, urinary tract obstruction, confusion and one seizure in the setting of a new central nervous system (CNS) metastasis. Grade III adverse events were seen in 43% of patients; common toxicities included grade I–II weight loss, diarrhoea, nausea, fatigue, anorexia, rash, hyperglycemia and anxiety/mood disorders.ConclusionsBuparlisib did not demonstrate significant activity in men with mCRPC, suggesting that PI3K inhibition is not sufficient to reverse resistant mCRPC progression. Future studies of PI3K pathway inhibitors with concurrent enzalutamide should develop optimal dosing and focus on selected patients more likely to benefit.     

Sunitinib malate for metastatic castration-resistant prostate cancer following docetaxel-based chemotherapy

BackgroundSystemic therapy options are limited for metastatic castration-resistant prostate cancer (CRPC) patients who progress following docetaxel (Taxotere). This phase II trial evaluated sunitinib malate in patients with progressing metastatic CRPC following prior docetaxel.Patients and methodsPatients with metastatic CRPC progressing following one to two chemotherapy regimens including docetaxel were included. The primary end point was progression-free survival (PFS) per radiographic and clinical evaluations. Oral sunitinib was administered 50 mg/day 4-weeks on followed by 2-weeks off per cycle up to a maximum of eight cycles or until clinical progression or intolerable toxicity.ResultsThirty-six patients with a median age of 69.5 years were accrued. The median PFS was 19.4 weeks with a 12-week PFS of 75.8%. Four patients (12.1%) had a ≥50% prostate-specific antigen (PSA) decline and seven (21.2%) had a ≥30% PSA decline. Two of 18 patients (11.1%) with measurable disease demonstrated 30% declines by RECIST and eight (44.4%) displayed some shrinkage. A decline in pain score ≥2 points occurred in 13.6% of 22 assessable patients. Drug discontinuation due to toxic effects occurred in 52.8% of patients.ConclusionSunitinib malate demonstrated promising activity in metastatic CRPC progressing after prior docetaxel.     

A phase I-II study of docetaxel and atrasentan in men with castration-resistant metastatic prostate cancer

PURPOSE: The primary aims of this phase I-II study were to determine the maximum tolerated dose, dose-limiting toxicity, pharmacokinetics, and preliminary efficacy of the combination of docetaxel and the endothelin A receptor antagonist atrasentan as first-line treatment for men with metastatic castration-resistant prostate cancer. EXPERIMENTAL DESIGN: Patients were treated with docetaxel at doses ranging from 60 to 75 mg/m(2) every 21 days, with daily oral atrasentan 10 mg starting on day 3. Patients were treated until evidence of disease progression or unacceptable toxicity. RESULTS: Thirty-one patients were enrolled over three docetaxel dose levels (8 at 60 mg/m(2), 19 at 70 mg/m(2), and 4 at 75 mg/m(2)) including dose expansion at 70 mg/m(2). The maximum tolerated dose of docetaxel was 70 to 75 mg/m(2). Drug-related grade 3-4 toxicities included neutropenia (50-63%) and febrile neutropenia (16-25%); other grade 1-2 toxicities included fatigue, peripheral edema, diarrhea, headache, rhinitis, anorexia, and nausea. Confirmed prostate-specific antigen (PSA) responses were observed in 23% [95% confidence interval (95% CI), 10-41%]; the rate of >30% declines in PSA was 35% (95% CI, 19-55%). Median overall survival was 17.6 months (95% CI, 13.0-23.2) and median progression-free survival was 4.2 months (95% CI, 2.3-5.8). Significant declines in bone alkaline phosphatase and serum N-telopeptides were observed with therapy. CONCLUSIONS: The maximum tolerated dose of every-3-week docetaxel with 10 mg atrasentan is 70 to 75 mg/m(2). Overall survival and progression-free survival are comparable to that seen with docetaxel and prednisone, whereas the rates of PSA decline are slightly lower than expected. A phase III study of this combination with prednisone has been initiated and is ongoing.     

Survival and PSA response of patients in the TAX 327 study who crossed over to receive docetaxel after mitoxantrone or vice versa

BackgroundThe TAX 327 study compared 3-weekly docetaxel, weekly docetaxel or 3-weekly mitoxantrone, each with prednisone, for 1006 patients with metastatic hormone-refractory prostate cancer. Survival and symptom control were superior following 3-weekly docetaxel as compared with mitoxantrone. At progression, many patients were treated with the other drug. Here, we provide a retrospective report of survival and prostate-specific antigen (PSA) response after second-line therapy.MethodsThe TAX 327 database provided information about treatment after progression on first-line therapy, and survival has been updated. Investigators were asked to provide information about crossover treatment and serial PSA values.ResultsWe identified 232 crossover patients. Median survival after crossover was 10 months and did not depend on direction of crossover. Data on PSA response are available for 96 patients: PSA response (≥50% reduction) occurred in 15% of 71 men receiving mitoxantrone after docetaxel and in 28% of 25 men receiving docetaxel after mitoxantrone. Median PSA progression-free survival was 3.4 months for mitoxantrone after docetaxel and 5.9 months for docetaxel after mitoxantrone.ConclusionsOne quarter of men received crossover therapy and survival was similar in the crossover groups. The PSA response rate to docetaxel after mitoxantrone was higher than that for mitoxantrone after docetaxel.     

A Phase 2 Trial of Abiraterone Followed by Randomization to Addition of Dasatinib or Sunitinib in Men With Metastatic Castration-Resistant Prostate Cancer

BackgroundResistance to novel androgen signaling inhibition and metastatic castration-resistant prostate cancer (mCRPC) progression is likely dependent on tumor microenvironment interactions. The Src pathway and neoangiogenesis have been implicated in prostate cancer progression. We studied the effect of adding the targeted agents dasatinib and sunitinib to abiraterone acetate (AA) in men with mCRPC.Patients and MethodsIn this open-label randomized phase 2 study, mCRPC patients received AA. At resistance to AA, they were randomized 1:1 to combination with dasatinib or sunitinib. At second progression, patients crossed over. The primary end point was time to treatment failure (TTF), defined as time to progression or death. Secondary end points included overall survival and safety.ResultsFrom March 2011 to February 2015, a total of 179 patients were enrolled and 132 subsequently randomized. Median TTF was 5.7 months in the dasatinib group and 5.5 months in the sunitinib group. There was no difference between the two groups in terms of TTF (hazard ratio, 0.85; 95% confidence interval, 0.59-1.22). Median overall survival from study entry was 26.3 months in the dasatinib group and 27.7 months in the sunitinib group (hazard ratio, 1.02; 95% confidence interval, 0.71-1.47). Grade 3 or higher adverse events related to study medication were more frequent with sunitinib (n = 44, 46%) compared to dasatinib (n = 26, 24%). At data cutoff, 7 patients were experiencing a continuous response to AA, with a median duration of treatment of 5.7 years.ConclusionThere is no difference in overall survival and TTF between dasatinib and sunitinib combined with abiraterone in the treatment of patients with bone mCRPC.     

Antitumour activity of docetaxel following treatment with the CYP17A1 inhibitor abiraterone: clinical evidence for cross-resistance?

BackgroundAbiraterone and docetaxel are both approved treatments for men with metastatic castration-resistant prostate cancer (mCRPC). Abiraterone pre-docetaxel is currently undergoing evaluation in a phase III study. In vitro studies indicate that taxanes may act by disrupting androgen receptor signalling. We hypothesised that prior abiraterone exposure would adversely impact docetaxel efficacy.Patients and methodsWe retrospectively evaluated activity of docetaxel in mCRPC patients previously treated with abiraterone, using Prostate Cancer Working Group and radiological criteria.ResultsOf the 54 patients treated with abiraterone, 35 subsequently received docetaxel. Docetaxel resulted in a prostate-specific antigen (PSA) decline of ≥50% in nine patients [26%, 95% confidence interval (CI) 13% to 43%], with a median time to PSA progression of 4.6 months (95% CI 4.2% to 5.9%). PSA declines ≥30% were achieved by 13 patients (37%, 95% CI 22% to 55%). The median overall survival was 12.5 months (95% CI 10.6–19.4). All patients who failed to achieve a PSA fall on abiraterone and were deemed abiraterone-refractory were also docetaxel-refractory (N = 8). In the 24 patients with radiologically evaluable disease, partial responses were reported in four patients (11%), none of whom were abiraterone-refractory.ConclusionThe activity of docetaxel post-abiraterone appears lower than anticipated and no responses to docetaxel were observed in abiraterone-refractory patients.     

A phase 2 study of patupilone in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel: Canadian Urologic Oncology Group study P07a

BackgroundThe purpose of this study was to determine the clinical activity of patupilone in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel.Patients and methods:Eligible patients had progressive disease within 6 months of receiving docetaxel. Patupilone was administered 10 mg/m² i.v. every 3 weeks. The primary end point was the proportion of patients with a confirmed ≥50% prostate-specific antigen (PSA) decline.ResultsEighty-three patients were enrolled. At baseline, the median time to progression after prior docetaxel was 1.4 months (range 0–5.7). Gastrointestinal serious adverse events occurred in four of the six initial patients leading to a reduction of the starting dose of patupilone to 8 mg/m² for subsequent patients. Grade 3–4 toxicity at this dose included diarrhea (22%), fatigue (21%), and anorexia (10%). One patient experienced grade 3–4 hematologic toxicity. A PSA decline of ≥50% occurred in 47% of patients. A partial measurable disease response occurred in 24% of assessable patients. A patient-reported pain response was observed in 59% of assessable patients. Median time to PSA progression was 6.1 months [95% confidence interval (CI) 4.7–8.0] and median overall survival was 11.3 months (95% CI 9.8–15.4).ConclusionsPatupilone at 8 mg/m² was tolerable, had antitumor activity, and was associated with symptomatic improvement in patients previously treated with docetaxel.     

A randomised non-comparative phase II trial of cixutumumab (IMC-A12) or ramucirumab (IMC-1121B) plus mitoxantrone and prednisone in men with metastatic docetaxel-pretreated castration-resistant prostate cancer

BackgroundCixutumumab, a human monoclonal antibody (HuMAb), targets the insulin-like growth factor receptor. Ramucirumab is a recombinant HuMAb that binds to vascular endothelial growth factor receptor-2. A non-comparative randomised phase II study evaluated cixutumumab or ramucirumab plus mitoxantrone and prednisone (MP) in metastatic castration-resistant prostate cancer (mCRPC).Patients and methodsMen with progressive mCRPC during or after docetaxel therapy received mitoxantrone 12 mg/m² on day 1 and prednisone 5 mg twice daily and were randomised 1:1 to receive either cixutumumab or ramucirumab 6 mg/kg intravenously weekly in a 21-day cycle. Primary end-point was composite progression-free survival (cPFS). Secondary end-points included safety, response, radiographic progression-free survival (PFS) and overall survival (OS). Sample size was based on a 50% increase in median cPFS from 2.6 (MP) to 3.9 months (either combination).Results132 men were treated (66 per arm). Median cPFS was 4.1 months (95% confidence interval (CI), 2.2–5.6) for cixutumumab and 6.7 months (95% CI, 4.5–8.3) for ramucirumab. Median time to radiographic progression was 7.5 months for cixutumumab and 10.2 months for ramucirumab, with a median OS of 10.8 and 13.0 months, respectively. Fatigue was the most frequent adverse event (AE). Incidence of most non-haematologic grade 3–4 AEs was <10% on both arms. Grade 3 cardiac dysfunction occurred in 7.6% of patients on ramucirumab.ConclusionCombinations of cixutumumab or ramucirumab plus MP were feasible and associated with moderate toxicities in docetaxel-pretreated men with mCRPC. Of the two regimens, the ramucirumab regimen is worthy of further testing based on the observed cPFS relative to the historical control.     

Prostate-specific antigen flare induced by cabazitaxel-based chemotherapy in patients with metastatic castration-resistant prostate cancer

BackgroundA prostate-specific antigen (PSA) flare occurs in about 15% of metastatic castration-resistant prostate cancer (mCRPC) patients receiving docetaxel. This flare has no standard definition. Its impact on treatment efficacy is unclear. We sought to evaluate the incidence and characteristics of PSA flare on cabazitaxel, and its impact on survival.MethodsMulticentre retrospective review of consecutive patients treated with cabazitaxel second-line chemotherapy for mCRPC. Collection of baseline characteristics, disease history and PSA levels before and during cabazitaxel therapy. Overall survival (OS) and radiological/clinical progression-free survival (PFS) for patient groups corresponding to different definitions of PSA flare estimated by the Kaplan–Meier method and compared using the log-rank test.ResultsOverall, 125 patients were included. Median PFS and OS were 6.5 and 13.3 months, respectively. Depending upon the definition used, flare incidence ranged from 8.3% to 30.6%. The flare lasted <2.6 months. A PSA flare followed by a ⩾50% decrease was associated with a median PFS and OS of 11.2 and 25.2 months, respectively. Median PFS and OS for a ⩾30% rather than ⩾50% decrease were 10.4 and 16.5 months. These outcomes were not significantly different from those in patients with immediate PSA decreases of ⩾50% or ⩾30% from baseline, but were significantly better than in patients experiencing no PSA decrease (p = 0.006 and 0.015, respectively, for OS).ConclusionThe PSA response to cabazitaxel, with or without initial flare, was associated with a strong survival benefit. The taxane-induced flare during the first 12 weeks of therapy can be ignored when evaluating PSA response.     

Second-Line Cabazitaxel Treatment in Castration-Resistant Prostate Cancer Clinical Trials Compared to Standard of Care in CAPRI: Observational Study in the Netherlands

BackgroundCabazitaxel has been shown to improve overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC) patients after docetaxel in the TROPIC trial. However, trial populations may not reflect the real-world population. We compared patient characteristics and outcomes of cabazitaxel within and outside trials (standard of care, SOC).Patients and MethodsmCRPC patients treated with cabazitaxel directly after docetaxel therapy before 2017 were retrospectively identified and followed to 2018. Patients were grouped on the basis of treatment within a trial or SOC. Outcomes included OS and prostate-specific antigen (PSA) response.ResultsFrom 3616 patients in the CAPRI registry, we identified 356 patients treated with cabazitaxel, with 173 patients treated in the second line. Trial patients had favorable prognostic factors: fewer symptoms, less visceral disease, lower lactate dehydrogenase, higher hemoglobin, more docetaxel cycles, and longer treatment-free interval since docetaxel therapy. PSA response (≥ 50% decline) was 28 versus 12%, respectively (P = .209). Median OS was 13.6 versus 9.6 months for trial and SOC subgroups, respectively (hazard ratio = 0.73, P = .067). After correction for prognostic factors, there was no difference in survival (hazard ratio = 1.00, P = .999). Longer duration of androgen deprivation therapy treatment, lower lactate dehydrogenase, and lower PSA were associated with longer OS; visceral disease had a trend for shorter OS.ConclusionPatients treated with cabazitaxel in trials were fitter and showed outcomes comparable to registration trials. Conversely, those treated in daily practice showed features of more aggressive disease and worse outcome. This underlines the importance of adequate estimation of trial eligibility and health status of mCRPC patients in daily practice to ensure optimal outcomes.