Effects of Reduction in Tumor Burden on Survival in Epithelioid Malignant Pleural Mesothelioma

Objective: To understand the relationship between response and survival in malignant pleural mesothelioma (MPM). Patients and Methods: The original clinical trial was conducted from April 1999 through March 2001. Patients with epithelioid MPM (n=305) were categorized using modified pleural Response Evaluation Criteria in Solid Tumors by whether they responded to treatment. Median progression-free survival (PFS) and overall survival (OS) were estimated and hazard ratios for responders and nonresponders were estimated and compared using the log-rank test. Multivariable Cox proportional hazards models were used to adjust for baseline prognostic factors. Results: Patients who responded to frontline therapy had a significantly longer OS (hazard ratio, 0.34; 95% CI, 0.24-0.49; median, 20.6 months; 95% CI, 15.3 months to not reached) than did those who did not respond (median, 9.4 months; 95% CI, 8.1-11.0 months) (P<.001). Similarly, responders had a significantly longer PFS (hazard ratio, 0.50; 95% CI, 0.39-0.64; median, 7.8 months; 95% CI, 6.5-8.5 months) than did nonresponders (median, 3.7 months; 95% CI, 2.9-4.3 months) (P<.001). These results were confirmed when adjusting for baseline prognostic factors. We also observed a survival benefit associated with disease stabilization in MPM. Conclusion: Our findings indicate that reduction in tumor burden or disease stabilization determined using modified pleural Response Evaluation Criteria in Solid Tumors is strongly associated with OS and PFS in epithelioid MPM.