Impact of Post-chemotherapy Radiotherapy on Survival Outcomes in Inoperable Malignant Mesothelioma: A Single-center Retrospective Analysis

Objective: Malignant pleural mesothelioma (MPM) is a rare and aggressive form of cancer with limited treatment options and a grim prognosis.While platinum-based chemotherapy remains the primary treatment for inoperable or metastatic disease, the role of radiotherapy (RT) in current treatment approaches remains incompletely defined.This study aimed to assess the effect of RT after first-line systemic chemotherapy on survival outcomes in patients with metastatic or inoperable malignant mesothelioma. Material and Methods:We conducted a retrospective review of the medical records of 58 patients with unresectable or metastatic MPM who were treated from January 2022 through December 2024 at a tertiary oncology center.All patients received platinum-pemetrexed-based first-line chemotherapy followed by pemetrexed maintenance.Based on post-treatment management, patients were categorized into RT and non-RT groups.Kaplan-Meier analyses were conducted to assess progression-free survival (PFS) and overall survival (OS), and statistical significance was assessed using the log-rank test.Results: RT was administered to 41.4% of patients after initial chemotherapy.The RT group showed a significantly longer median PFS (14.1 months) compared with the non-RT group (9.7 months) [hazard ratio (HR): 0.34; 95% confidence interval (CI): 0.16-0.73;p<0.045].Similarly, median OS was notably longer in the RT group (24.6 months vs. 14.5 months; HR: 0.55; 95% CI: 0.31-0.72;p<0.003).Moreover, a greater proportion of RT patients received secondline immunotherapy.No grade 3 RT-related toxicities were observed. Conclusion:RT after first-line chemotherapy may provide a survival advantage in certain patients with metastatic or inoperable mesothelioma, particularly when incorporated into sequential treatment plans that include immunotherapy.Further prospective studies are necessary to validate these results and improve patient selection.