Mesothelioma showdown: Surgery vs. chemo—When the numbers don’t agree.

e20093 Background: Malignant mesothelioma is an aggressive malignancy with limited treatment options and poor survival outcomes. This study compares 4-year observed survival rates among two therapeutic groups: chemotherapy followed by surgery (CTX/Surg), and chemotherapy alone (CTX). Our findings were contextualized in light of MARS study, which examined similar therapeutic approaches and provide further insight into these findings. Methods: We performed a retrospective cohort study using the SEER Research Plus Database, 17 registries, (Nov 2022, Sub 2000-2020) to evaluate the overall survival (OS) of stage II and III mesothelioma cases in the U.S. during the 2004–2017 period. This timeframe aligns with the 17 registries where staging data were reported by SEER. Propensity score matching was used to adjust for potential confounders. The study included malignant mesothelioma of all histological types—epithelioid, sarcomatoid, and biphasic. Cases diagnosed outside the 2004–2017 period or with stages other than II and III were excluded. The 48-month OS was determined for each treatment group. Survival analysis was performed using the Kaplan-Meier method, and hazard ratios (HRs) with corresponding confidence intervals (CIs) were derived using multivariable Cox proportional hazards regression and evaluated with the log-rank test. Results: Among patients with stage II and III mesothelioma, the CTX/Surg group (n = 44) demonstrated a 4-year OS of 19% with a median survival of 24 months, compared to a 4-year OS of 16.6% and median survival of 19 months in the CTX group (n = 121). While these results suggest a survival trend favoring CTX/Surg, the difference was not statistically significant (p = 0.274). The hazard ratio for the CTX group relative to CTX/Surg was 1.167 (95% CI: 0.43–3.14), further underscoring the lack of statistical significance after adjusting for confounders. Conclusions: Although our findings indicate a numerical survival advantage with CTX/Surg, the lack of statistical significance challenges its superiority as a treatment strategy. These results diverge from prior studies, such as MARS, which questioned the role of surgery, highlighting the complexity of optimizing treatment approaches. Immunotherapy has become widely available for mesothelioma in recent years, which will potentially alter the survival curve dynamics, however, its impact within this timeframe requires further investigation. Future research should prioritize refining patient selection criteria and exploring the evolving role of surgery within the context of multimodal therapy for mesothelioma.