Patient selection for surgery for peritoneal sarcomatosis in retroperitoneal sarcoma —— external validation of the Simplified Peritoneal Sarcomatosis Score

Abstract Background Peritoneal sarcomatosis (PS) in patients with retroperitoneal sarcoma (RPS) often indicates a poor prognosis. The Simplified Peritoneal Sarcomatosis Score (SPSS) had been devised as a simple tool to stratify such patients. This study aimed to validate the effectiveness of SPSS and attempted to explore factors predicting surgical outcomes. Methods Patients with PS in RPS who underwent surgery between January 2011 and January 2019 were retrospectively analyzed. Survival analyses were performed to analyze SPSS, together with other factors such as completeness of surgery, surgical history and pathological types. Results A total of 49 patients were included, 34 of whom underwent macroscopically complete excision (CE) successfully. Eighteen and 31 patients were considered SPSS-L (low) and SPSS-H (high), respectively. The median follow-up time was 36.0 months. In univariate analysis, both SPSS and completeness of surgery showed obvious influences on survival. Compared to SPSS-H patients, SPSS-L patients had a significantly longer median overall survival (OS) (27 vs. 10 months; P = 0.03) and progression-free survival (PFS) (14 vs. 8 months, P = 0.021). Similarly, patients who underwent CE had superior median OS (20 vs. 8 months, P = 0.022) and PFS (14 vs. 8 months, P = 0.027) than those who underwent imcomplete excision. In multivariate analysis, completeness of surgery was shown to be the only independent predictor of both OS (P = 0.037) and PFS (P = 0.027). Conclusions SPSS is a useful tool to stratify RPS patients with PS, while achievement of CE is the key factor to improving their prognosis.