Efficacy of postoperative immunotherapy on MPM patients after CRS + HIPEC: A single-center retrospective study based on propensity score matching.

To investigate the efficacy of postoperative immunotherapy in patients with malignant peritoneal mesothelioma (MPM) after cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC). The clinical data of 160 MPM patients who underwent CRS + HIPEC at our center from April 2015 to February 2024 were retrospectively analyzed. All patients received postoperative chemotherapy and were divided into the Chemo-only group and the Immunotherapy group according to whether they received postoperative immunotherapy or not. Propensity score matching (PSM) was used to match baseline characteristics. The median overall survival (OS) was compared between the two groups. The Cox regression model was used to determine the independent prognostic factors, and subgroup analysis was performed to calculate the interaction. After matching, a total of 70 patients were included for final analysis, consisting of 35 patients each in the Chemo-only and Immunotherapy groups. Survival analysis showed that the median OS was significantly longer in the Immunotherapy group than the Chemo-only group (not-reached [NR] vs. 28.4 months) (p = 0.001). Univariate and multivariate Cox analyses indicated that postoperative immunotherapy was an independent protective factor for OS. Furthermore, subgroup analysis suggested that the results were generally robust, with no significant interactions. The median OS of sintilizumab was probably superior to camrelizumab (NR vs. 40.0 months, p = 0.052) and significantly longer than other immunotherapy regimens (pembrolizumab, cardunnilumab, nivolumab+ipilimumab) (NR vs. 26.7 months, p = 0.008). Postoperative immunotherapy, when compared to postoperative chemotherapy alone, could enhance the survival of MPM patients following CRS + HIPEC.