Microsatellite instability should not determine candidacy for cytoreductive surgery and hyperthermic intraperitoneal chemoperfusion in patients with peritoneal metastases from colorectal cancer

Background: Cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) is a multimodal therapeutic option for the management of peritoneal metastases (PM). Treatment outcomes for patients with colorectal cancer (CRC) PM undergoing CRS+HIPEC with microsatellite instability (MSI) remain unknown. We examined the patient characteristics and outcomes in patients with MSI CRC after CRS +HIPEC. Methods: This was a retrospective cohort study of a prospectively maintained database of all patients with CRC PM undergoing CRS+HIPEC (2010-2020). Categorical and continuous variables were analyzed using the chi-square test and independent samples t test, respectively. Survival was evaluated with the Kaplan-Meier analysis. Results: There were 324 patients diagnosed as having CRC PM undergoing CRS+HIPEC (MSI, n = 23; microsatellite stable [MSS], n = 301). There was no statistically significant difference in patient demographics, tumor characteristics, or perioperative factors between the 2 groups. There was a trend toward improved survival in the MSI group with a median overall survival (OS) of 96.7 month compared with patients with MSS disease (median OS, 51.4 months; P = .10). Patients with MSI demonstrated median progression-free survival (PFS) 8.5 months compared with 11.4 months in the MSS cohort (P = .28). Conclusion: Patients with CRC PM, regardless of MSI or MSS status, demonstrate similar OS and PFS after CRS+HIPEC. MSI status should not change a patient's candidacy for CRS+HIPEC. (c) 2024 Published by Elsevier Inc. on behalf of Society for Surgery of the Alimentary Tract.