Response to treatment series: part 2, tumor response assessment--using new and conventional criteria

OBJECTIVE: Conventional anatomic imaging biomarkers, including World Health Organization (WHO) criteria and Response Evaluation Criteria in Solid Tumors (RECIST), although effective, have limitations. This article will discuss the conventional and newer morphologic imaging biomarkers for the assessment of tumor response to therapy. CONCLUSION: Applying established methods of assessing tumor response to therapy allows consistency in image interpretation and facilitates communication with oncologists. Because of the new methods of treatment, assessment of necrosis and volumetric information will need to be incorporated into size-based criteria.     

Imaging of response to treatment in oncology

Imaging plays a crucial role in oncology to assist in the management of patients and selection of drug regimen. Recent advances in imaging techniques allowing to predict and evaluate response to treatments in oncology will be reviewed. The standard in the evaluation of response to treatment is based on the measurement of lesion size. Functional imaging assesses physiological or molecular processes that may be earlier indicators of early response to treatment. Dynamic imaging of tumor vascularization assesses the biodistribution of a contrast agent within tumoral tissues. Diffusion-weighted MR imaging can differentiate free water from water restricted by tissues, providing an assessment of tumor cellularity. MR spectroscopy assesses the relative quantity of specific chemical components within normal and tumoral tissues. 18 FDG PET imaging provides an assessment of the metabolic activity of tissues. FDG uptake is proportional to cellular proliferation and number of viable cells within a tumor. Results from studies assessing the role of these emerging imaging techniques remain preliminary and the medical community must determine their respective role in the routine evaluation of response to treatment in oncological patients.     

The use of Deauville criteria in follow-up assessment of response to therapy in extra-nodal Non-Hodgkin's lymphoma

Objective

Our aim was evaluate the role the PET/CT in the assessment of response to therapy in patients with Non-Hodgkin extra-nodal lymphoma: in particular, a five-point scale (Deauville criteria), which can be employed for early- and late-therapeutic response assessment.

Evaluating tumor response with FDG PET: updates on PERCIST,comparison with EORTC criteria and clues to future developments

Eighteen years ago, the EORTC PET criteria standardized for the first time response assessment by FDG PET. Response assessment by FDG PET has been further developed and refined by PERCIST (PET response criteria in solid tumors). This review describes the data underlying these two systems for assessing tumor response on FDG PET/CT. It also summarizes recent clinical studies that have compared EORTC criteria and PERCIST with each other as well as with the anatomically based “response criteria in solid tumors” (RECIST). These studies have shown that response assessment by EORTC criteria and PERCIST leads to very similar response classifications. In contrast, there are significant differences between response assessment by PERCIST and RECIST. Preliminary data also suggest that response assessment by PERCIST is better correlated with patient outcome and may be a better predictor for the effectiveness of new anti-cancer therapies than RECIST. If correct, this could have a significant impact on oncologic drug development. However, confirmation of the better predictive value of response assessment by PERCIST by data from randomized trials is still lacking.     

Role of functional magnetic resonance imaging in assessing metastatic leiomyosarcoma response to chemoembolization

PURPOSE: To assess the value of functional magnetic resonance (MR) imaging in the evaluation of early tumor response after transarterial chemoembolization (TACE) for metastatic leiomyosarcoma and compare tumor response using functional MR imaging versus traditional imaging response assessment, which is based on tumor size. MATERIALS AND METHODS: We evaluated 31 lesions in 10 patients with liver metastases from leiomyosarcoma using MR imaging studies before and after TACE. Diffusion and contrast-enhanced MR imaging was performed on a 1.5-T unit. Imaging protocol consisted of T2-weighted fast spin-echo images, breath-hold diffusion-weighted echo-planar images, and breath-hold unenhanced and contrast-enhanced T1-weighted 3-dimensional fat-suppressed spoiled gradient-echo images in the arterial phase (20 seconds) and portal venous phase (60 seconds). Parameters evaluated included change in tumor size, enhancement, and apparent diffusion coefficient (ADC) values. Median survival was also calculated for the entire cohort. RESULTS: The 31 lesions evaluated had a mean size of 4.8 cm before treatment. Tumor size decreased only by 2% immediately after treatment. Decrease of tumor enhancement after treatment was significant (P < 0.0001) in the arterial phase (69%) as well as in the portal venous phase (64%). After TACE, mean tumor ADC increased by 20% (P = 0.0015), whereas mean nontreated liver, spleen, and muscle ADC values did not change significantly (P = 0.44, P = 0.287, and P = 0.098, respectively). Patient survival from time of first TACE was 21 months for the entire cohort. CONCLUSION: In patients with leiomyosarcoma and liver metastases who were treated with TACE, significant early changes in the treated lesions occurred on functional MR imaging. These include decrease in tumor enhancement and increase in tumor ADC value, suggesting increasing tumor necrosis and cell death. Changes in tumor size were small and inadequate to assess treatment response, suggesting limitation of the current response criteria in the early assessment of tumor response.     

Tumor response and clinical outcome in metastatic gastrointestinal stromal tumors under sunitinib therapy: Comparison of RECIST,Choi and volumetric criteria

Purpose

Purpose of the study was to compare radiological treatment response according to RECIST, Choi and volumetry in GIST-patients under 2nd-line-sunitinib-therapy and to correlate the results of treatment response assessment with disease-specific survival (DSS).

Patients and methods

20 patients (mean: 60.7 years; 12 male/8 female) with histologically proven GIST underwent baseline-CT of the abdomen under imatinib and follow-up-CTs 3 months and 1 year after change to sunitinib. 68 target lesions (50 hepatic, 18 extrahepatic) were investigated. Therapy response (partial response (PR), stable disease (SD), progressive disease (PD)) was evaluated according to RECIST, Choi and volumetric criteria. Response according to the different assessment systems was compared and correlated to the DSS of the patients utilizing Kaplan–Meier statistics.

Results

The mean DSS (in months) of the response groups 3 months after therapy change was: RECIST: PR (0/20); SD (17/20): 30.4 (months); PD (3/20) 11.6. Choi: PR (10/20) 28.6; SD (8/20) 28.1; PD (2/20) 13.5. Volumetry: PR (4/20) 29.6; SD (11/20) 29.7; PD (5/20) 17.2.Response groups after 1 year of sunitinib showed the following mean DSS: RECIST: PR (3/20) 33.6; SD (9/20) 29.7; PD (8/20) 20.3. Choi: PR (10/20) 21.5; SD (4/20) 42.9; PD (6/20) 23.9. Volumetry: PR (6/20) 27.3; SD (5/20) 38.5; PD (9/20) 19.3.

Conclusion

One year after modification of therapy, only partial response according to RECIST indicated favorable survival in patients with GIST. The value of alternate response assessment strategies like Choi criteria for prediction of survival in molecular therapy still has to be demonstrated.     

Personalized Oncology in Interventional Radiology

As personalized medicine becomes more applicable to oncologic practice, image-guided biopsies will be integral for enabling predictive and pharmacodynamic molecular pathology. Interventional radiology has a key role in defining patient-specific management. Advances in diagnostic techniques, genomics, and proteomics enable a window into subcellular mechanisms driving hyperproliferation, metastatic capabilities, and tumor angiogenesis. A new era of personalized medicine has evolved whereby clinical decisions are adjusted according to a patient’s molecular profile. Several mutations and key markers already have been introduced into standard oncologic practice. A broader understanding of personalized oncology will help interventionalists play a greater role in therapy selection and discovery.     

Inter-operator variability and source of errors in tumour response assessment for hepatocellular carcinoma treated with sorafenib

Objectives

To assess the inter-operator concordance and the potential sources of discordance in defining response to sorafenib in hepatocellular carcinoma (HCC).

Methods

All patients who received sorafenib between September 2008 and February 2015 were scrutinised for this retrospective study. Images were evaluated separately by three radiologists with different expertise in liver imaging (operator 1, >10 years; operator 2, 5 years; operator 3, no specific training in liver imaging), according to: response evaluation radiological criteria in solid tumours (RECIST) 1.1, modified RECIST (mRECIST) and response evaluation criteria in cancer of the liver (RECICL).

Results

The overall response concordance between the more expert operators was good, irrespective of the criteria (RECIST 1.1, ? = 0.840; mRECIST, ? = 0.871; RECICL, ? = 0.819). Concordance between the less expert operator and the other colleagues was lower. The most evident discordance was in target lesion response assessment, with expert operators disagreeing mostly on lesion selection and less expert operators on lesion measurement. As a clinical correlate, overall survival was more tightly related with “progressive disease” as assessed by the expert compared to the same assessment performed by operator 3.

Conclusions

Decision on whether a patient is a responder or progressor under sorafenib may vary among different operators, especially in case of a non-specifically trained radiologist. Regardless of the adopted criteria, patients should be evaluated by experienced radiologists to minimise variability in this critical instance.

Key Points

? Inter-operator variability in the assessment of response to sorafenib is poorly known. ? The concordance between operators with expertise in liver imaging was good. ? Target lesions selection was the main source of discordance between expert operators. ? Concordance with non-specifically trained operator was lower, independently from the response criteria. ? The non-specifically trained operator was mainly discordant in measurements of target lesions.

     

18F-FDG-PET/CT in assessing response to neoadjuvant chemoradiotherapy for potentially resectable locally advanced esophageal cancer

Purpose

To correlate metabolic response to neoadjuvant chemoradiotherapy (NACR) on FDG-PET/CT using PERCIST-based criteria to pathologic and clinical response, and survival in patients with locally advanced esophageal cancer (LAEC).

Materials and methods

Forty-five patients with LAEC underwent PET/CT at baseline and after NACR. Tumors were evaluated using PERCIST (PET response criteria in solid tumors)-based criteria including SUL, SUL tumor/liver ratio, % change in SUL. These parameters were compared to pathology regression grade (PRG), clinical response (including residual or new disease beyond the surgical specimen), and overall survival.

Results

On surgical pathology, there was complete or near-complete regression of tumor in 51.1 %, partial response in 42.2 %, and lack regression in 4.4 %. One patient (2.2 %) had progression of disease on imaging and did not undergo surgical resection. None of the baseline PET parameters had significant correlation to pathology regression grade or clinical response. On follow-up, a positive correlation was found between post-therapy SUL ratio, %? SUL and %? SUL ratio and clinical response (p = 0.025, 0.035, 0.030, respectively). A weak correlation was found between post-therapy SUL ratio to PRG (p = 0.049). A strong correlation was found between the metabolic response score and PRG (p = 0.002) as well as between metabolic response and clinical response (p < 0.001).

Conclusion

PERCIST-based metabolic response assessment to NACR in LAEC may correlate with clinical outcome and survival.     

Quantitative magnetic resonance imaging (q-MRI) for the assessment of soft-tissue sarcoma treatment response: a narrative case review of technique development

Soft-tissue sarcomas are a heterogeneous class of tumors that exhibit varying degrees of cellularity and cystic degeneration in response to neoadjuvant chemotherapy. This creates unique challenges in the radiographic assessment of treatment response when relying on conventional markers such as tumor diameter (RECIST criteria). In this case series, we provide a narrative discussion of technique development for whole tumor volume quantitative magnetic resonance imaging (q-MRI), highlighting cases from a small pilot study of 8 patients (9 tumors) pre- and post-neoadjuvant chemotherapy. One of the methods of q-MRI analysis (the “constant-cutoff” technique) was able to predict responders versus non-responders based on percent necrosis and viable tumor volume calculations (p = 0.05), respectively. Our results suggest that q-MRI of whole tumor volume contrast enhancement may have a role in tumor response assessment, although further validation is needed.     

Radiological measurement of breast cancer metastases to lung and liver: comparison between WHO (bidimensional) and RECIST (unidimensional) guidelines

PURPOSE: Radiologic assessment of "response-to-treatment" during clinical trials of anticancer drugs has been conventionally based on bidirectional tumor measurement. Recently, the revised guidelines were published, which recommended unidirectional tumor measurements. The purpose of this study was to compare response to treatment between the two measurement techniques in breast cancer patients with lung and liver metastases. METHOD: Contrast-enhanced computed tomography studies of 86 breast cancer patients who had lung (n = 27) and liver (n = 59) metastases and who were enrolled in a phase-III oncology trial were evaluated before initiation of treatment and at 6 months after treatment. Lesions were measured by subspecialist radiologists on digitized images using electronic calipers. The largest diameter of the lesions was extracted from bidimensional measurements. Response to treatment was categorized into one of four categories: complete response indicating lesion disappearance, partial response indicating >30% decrease in tumor diameter, or >50% reduction in tumor area, disease progression indicating >20% increase in tumor diameter, or >25% increase in tumor area, and stable disease (neither complete response, partial response, nor disease progression). Response to treatment between the two measurement techniques was compared statistically using the chi2 test. RESULTS: Response to treatment was concordant in 76 patients between unidimensional and bidimensional measurement techniques. In 5 patients (2 lung and 3 liver metastases) the response assessment was improved using unidimensional criteria and in 5 patients (2 lung and 3 liver metastases) the response was worse using unidimensional guidelines. Thus, the overall response rate was 50% for both unidimensional and bidimensional measurement techniques. There was no statistical difference between the two techniques. CONCLUSION: Unidimensional measurements are appropriate for measuring the size of liver and lung metastases for determining response to treatment during clinical testing of oncologic drugs.     

CT tumor measurement for therapeutic response assessment: comparison of unidimensional,bidimensional, and volumetric techniques initial observations

PURPOSE: To compare unidimensional, bidimensional, and volumetric techniques for evaluation of treatment response in patients with liver metastases from breast cancer in a phase III clinical trial. MATERIALS AND METHODS: Helical computed tomographic (CT) studies in 38 patients with liver metastases from breast cancer who were enrolled in a phase III clinical trial were evaluated before treatment and at 6 months after treatment. Two subspecialty radiologists measured all lesions on transverse CT scans with use of electronic calipers according to both unidimensional and bidimensional criteria. Volumetric measurements were made by tracing individual lesions. Measurements of individual lesions were summed to obtain patient response, which was categorized as complete response, disappearance of lesions; partial response, greater than 30% decrease in tumor diameter (unidimensional), greater than 50% reduction in tumor area (bidimensional), or greater than 65% reduction in tumor volume (volumetric); disease progression, greater than 20% increase in tumor diameter, greater than 25% increase in tumor area, or greater than 73% increase in tumor volume: or stable disease (size response other than that of complete response, partial response, or disease progression). RESULTS: In 37 patients, there was concordant treatment response with use of unidimensional and bidimensional techniques. Volumetric measurement produced results different from those of the unidimensional and bidimensional techniques in 12 and 13 patients, respectively. In six patients with partial response per unidimensional and bidimensional criteria, the response based on the volumetric technique was stable disease. In two patients with stable disease per bidimensional and unidimensional criteria, the response was partial response by volumetric measurement. In four patients with disease progression per bidimensional and unidimensional criteria, the response was stable disease per volumetric criteria. CONCLUSION: Volumetric measurement of tumor burden gives different results for treatment response compared with that of the unidimensional or bidimensional technique in a considerable proportion of patients.     

Automatic multi-modal MR tissue classification for the assessment of response to bevacizumab in patients with glioblastoma

Background

Current methods for evaluation of treatment response in glioblastoma are inaccurate, limited and time-consuming. This study aimed to develop a multi-modal MRI automatic classification method to improve accuracy and efficiency of treatment response assessment in patients with recurrent glioblastoma (GB).

Materials and methods

A modification of the k-Nearest-Neighbors (kNN) classification method was developed and applied to 59 longitudinal MR data sets of 13 patients with recurrent GB undergoing bevacizumab (anti-angiogenic) therapy. Changes in the enhancing tumor volume were assessed using the proposed method and compared with Macdonald's criteria and with manual volumetric measurements. The edema-like area was further subclassified into peri- and non-peri-tumoral edema, using both the kNN method and an unsupervised method, to monitor longitudinal changes.

Results

Automatic classification using the modified kNN method was applicable in all scans, even when the tumors were infiltrative with unclear borders. The enhancing tumor volume obtained using the automatic method was highly correlated with manual measurements (N = 33, r = 0.96, p < 0.0001), while standard radiographic assessment based on Macdonald's criteria matched manual delineation and automatic results in only 68% of cases. A graded pattern of tumor infiltration within the edema-like area was revealed by both automatic methods, showing high agreement. All classification results were confirmed by a senior neuro-radiologist and validated using MR spectroscopy.

Conclusion

This study emphasizes the important role of automatic tools based on a multi-modal view of the tissue in monitoring therapy response in patients with high grade gliomas specifically under anti-angiogenic therapy.     

Quantitative assessment of tumor metabolism using FDG-PET imaging

Positron emission tomography using the glucose analog fluorine-18 fluorodeoxyglucose (FDG-PET) provides a unique means of non-invasive assessment of tumor metabolism. Several approaches, of varying complexity, can be applied for quantitative image analysis. Previous studies have demonstrated that "standardized uptake values" (SUV) and simplified tracer kinetic modeling, using the "Patlak-Gjedde"-analysis, provide highly reproducible parameters of tumor glucose utilization. Quantification of regional FDG uptake gives complementary information to visual image interpretation and provides objective criteria for differentiation between benign and malignant lesions. Moreover, quantification of tumor glucose metabolism is essential for assessment of therapy induced changes. Clinical studies in breast cancer and lymphoma suggest that serial FDG-PET studies allow the prediction of response early in the course of chemotherapy. Therefore, FDG-PET may be helpful in patient management by avoiding ineffective chemotherapy and supporting the decision to continue dose intense regimes. In addition, FDG-PET allows non-invasive assessment of tumor viability following chemo- and radiotherapy which permits individualized therapy management.     

Neue bildgebende Strategien zum Monitoring molekularer Pharmakotherapien bei GIST

Prognosis and clinical management of patients with gastrointestinal stromal tumors (GIST) has changed significantly with the introduction of new molecular-targeted drugs such as imatinib. This development is accompanied by a need to re-evaluate the established imaging criteria used to assess treatment response. The frequently used response evaluation criteria in solid tumors (RECIST) are mainly based on one-dimensional tumor size and do not take into account functional changes in responding GISTs such as a decrease in CT density or in the number of intratumoral vessels. Positron emission tomography (PET) has been found to be highly sensitive in detecting early response and to have a predictive value in the long term response to imatinib treatment. Monitoring the course of the disease by PET is limited due to scanner availability and economic constraints. Modified CT response criteria using a combination of tumor density and tumor size are especially promising in early response assessment and have a good prognostic value. Further optimization of existing response criteria and evaluation of new candidate markers of treatment response, such as quantitative perfusion will be the key for optimized monitoring of targeted therapies in GIST.     

肿瘤免疫治疗疗效评价标准—iRECIST解读

近年来,肿瘤免疫治疗迅猛发展,而现有世界卫生组织标准或实体瘤疗效评价标准(response evaluation criteria in solid tumor,RECIST)无法对免疫治疗疗效进行准确的解读和确切的评估,尤其是反映肿瘤缓解或进展的关键问题—肿瘤负荷的变化。基于此,RECIST工作组结合临床肿瘤免疫治疗实践改良的实体肿瘤疗效评价标准（RECIST版本1.1）制定了一个新的肿瘤免疫治疗疗效评价标准—实体瘤免疫治疗疗效评价标准（immune response evaluation criteria in solid tumor,iRECIST）,并在2017年第18期的The Lancet Oncology上发表。该标准详细定义了实体瘤测量及肿瘤大小评价的标准方法,以期在后续肿瘤免疫治疗临床试验中得以验证。作者对这一新的标准作一介绍。     

Volumetric assessment of tumor size changes in pediatric low-grade gliomas: feasibility and comparison with linear measurements

Purpose

We report a retrospective comparison between bi-dimensional RANO criteria and manual volumetric segmentation (MVS) in pediatric low-grade gliomas.

Methods

MRI FLAIR or T1 post contrast images were used for assessment of tumor response. Seventy patients were included in this single center study, for each patient two scans were assessed (“time 0” and “end of therapy”) and response to therapy was evaluated for both methods. Inter-reader variability and average time for volumetric assessment were also calculated.

Results

Fourteen (20%) of the 70 patients had discordant results in terms of response assessment between the bi-dimensional measurements and MVS. All volumetric response assessments were in keeping with the subjective analysis of tumor (radiology report). Of the 14 patients, 6 had stable disease (SD) on MVS and progressive disease (PD) on 2D assessment, 5 patients had SD on MVS and partial response (PR) on 2D assessment, 2 patients had PD on MVS and SD on 2D assessment, and 1 patient had PR on MVS and SD on 2D analysis. The number of discordant results rises to 21(30%) if minor response is integrated in the response assessment. MVS was relatively fast and showed high inter-reader concordance.

Conclusion

Our analysis shows that therapeutic response classification may change in a significant number of children by performing a volumetric tumor assessment. Furthermore, MVS is not particularly time consuming and has very good inter-reader concordance.

     

Imaging-Based Tumor Treatment Response Evaluation: Review of Conventional, New, and Emerging Concepts

Tumor response may be assessed readily by the use of Response Evaluation Criteria in Solid Tumor version 1.1. However, the criteria mainly depend on tumor size changes. These criteria do not reflect other morphologic (tumor necrosis, hemorrhage, and cavitation), functional, or metabolic changes that may occur with targeted chemotherapy or even with conventional chemotherapy. The state-of-the-art multidetector CT is still playing an important role, by showing high-quality, high-resolution images that are appropriate enough to measure tumor size and its changes. Additional imaging biomarker devices such as dual energy CT, positron emission tomography, MRI including diffusion-weighted MRI shall be more frequently used for tumor response evaluation, because they provide detailed anatomic, and functional or metabolic change information during tumor treatment, particularly during targeted chemotherapy. This review elucidates morphologic and functional or metabolic approaches, and new concepts in the evaluation of tumor response in the era of personalized medicine (targeted chemotherapy).     

CT-based response assessment of advanced gastrointestinal stromal tumor: Dual energy CT provides a more predictive imaging biomarker of clinical benefit than RECIST or Choi criteria

Objectives

Dual-energy CT (DECT) allows quantification of intravenously injected iodinated contrast media in tumors, and therefore may be considered as a surrogate marker for perfusion and tumor vascularity. This study evaluated whether newly developed DECT response criteria allow better correlation with survival than established response criteria.

Methods

Seventeen patients with advanced GIST treated with tyrosine-kinase-inhibitors were assessed by contrast-enhanced DECT 2 and 6 months after beginning of treatment. Response to treatment of 165 tumor lesions was evaluated according to RECIST, Choi criteria and newly developed DECT criteria, defining non-responders as an increase of both tumor size >20% and iodine related attenuation or either a >50% increase of tumor size or iodine related attenuation. All other patients were classified as responders. Progression-free survival (PFS) and overall survival (OS) were calculated by Kaplan–Meier analysis.

Results

Choi criteria and DECT showed a significantly longer median PFS of patients rated as responders than patients rated as non-responders (9–29 months vs. 2–6 months; p < 0.02) at follow-up. Only DECT analysis at 6 months follow-up allowed a valid prediction of OS.

Conclusion

This study indicates that DECT allows a better prediction of therapeutic benefit in advanced GIST patients treated with tyrosine-kinase-inhibitors than established response criteria. However, the most important predictive biomarker of therapeutic benefit was absence of progression, no matter which response evaluation criteria were applied.     

Early prediction of response to chemotherapy and survival in malignant pleural mesothelioma using a novel semiautomated 3-dimensional volume-based analysis of serial 18F-FDG PET scans.

The aim of chemotherapy for mesothelioma is to palliate symptoms and improve survival. Measuring response using CT is challenging because of the circumferential tumor growth pattern. This study aims to evaluate the role of serial (18)F-FDG PET in the assessment of response to chemotherapy in patients with mesothelioma. METHODS: Patients were prospectively recruited and underwent both (18)F-FDG PET and conventional radiological response assessment before and after 1 cycle of chemotherapy. Quantitative volume-based (18)F-FDG PET analysis was performed to obtain the total glycolytic volume (TGV) of the tumor. Survival outcomes were measured. RESULTS: Twenty-three patients were suitable for both radiological and (18)F-FDG PET analysis, of whom 20 had CT measurable disease. After 1 cycle of chemotherapy, 7 patients attained a partial response and 13 had stable disease on CT assessment by modified RECIST (Response Evaluation Criteria in Solid Tumors) criteria. In the 7 patients with radiological partial response, the median TGV on quantitative PET analysis fell to 30% of baseline (range, 11%-71%). After 1 cycle of chemotherapy, Cox regression analysis demonstrated a statistically significant relationship between a fall in TGV and improved patient survival (P = 0.015). Neither a reduction in the maximum standardized uptake value (P = 0.097) nor CT (P = 0.131) demonstrated a statistically significant association with patient survival. CONCLUSION: Semiquantitative (18)F-FDG PET using the volume-based parameter of TGV is feasible in mesothelioma and may predict response to chemotherapy and patient survival after 1 cycle of treatment. Therefore, metabolic imaging has the potential to improve the care of patients receiving chemotherapy for mesothelioma by the early identification of responding patients. This technology may also be useful in the assessment of new systemic treatments for mesothelioma.