The role of volumetric method in the assessment of chemotherapy response and predicting survival in malignant pleural mesothelioma

Background: Malignant pleural mesothelioma (MPM) is a pleural tumor with high mortality rate and short-term survival expectancy after diagnosis. Assessment of the response to chemotherapy, which is the first choice in treatment of MPM, is important for the transition to alternative chemotherapy protocols and immunotherapy. There is no clarity in the response to chemotherapy treatment. Objective: Our study aims to compare the assessment of chemotherapy response using the Modified Response Evaluation Criteria in Solid Tumors (mRECIST) criteria and volumetric measurements and to correlate with median survival. Materials and Methods: Thirty-two patients (16 females and 16 males) were included in the study, and their ages ranged from 28 to 78 years. Chemotherapy response was determined by both mRECIST and volumetric approach. Tumor volume was measured by linear interpolation and semi-automatic segmentation. Log-rank multiple cutoff analysis was used to determine appropriate cutoff values of volumetric response criteria. Results: According to both mRECIST and volumetric approach, median survival times in partial response, stable disease, and progressive disease groups were 24, 15, and 9 months, respectively. The survival times of the three groups were different (logrank: 17.76; P < 0.001) by mRECIST. The survival of the progressive disease group was shorter than that of the other groups (logrank: 18.91; P < 0.001) by volumetric approach. Conclusions: In the assessment of chemotherapy response, even though classifications obtained according to the mRECIST criteria and volumetric measurements are statistically compatible, we think that the measurement of the volumetric values will increase the standardization. In our study, threshold values for volumetric measurements were determined; however, these values should be supported by large-scale multicenter studies.