Abstract: Objective To investigate the effect of primary tumor location on perioperative complications and long⁃term prognosis in colorectal cancer patients with peritoneal metastasis (PM) undergoing cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC). Methods Baseline data, clinicopathological characteristics, perioperative data, and prognosis were retrospectively collected from patients with colorectal cancer PM treated CRS combined with HIPEC at the Department of Colorectal Surgery, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College between June 2017 and December 2022. Kaplan⁃Meier method was used to draw the survival curve, and Log⁃rank was used to compare the survival differences between groups. Univariable and multivariable Cox regression analysis were used to analyze the influencing factors of overall survival (OS) in patients with colorectal cancer PM treated with CRS combined with HIPEC. Results A total of 142 patients were enrolled, with 104 in the colon cancer group and 38 in the rectal cancer group. Compared with colon cancer PM patients, rectal cancer PM patients demonstrated higher incidence of grade 3-4 complications (19.2% vs 36.8%, P=0.029), and worse 3⁃year OS (47.9% vs 22.7%, P=0.003) after CRS+HIPEC. The location of the primary tumor in the rectum (HR=2.07, 95%CI: 1.07-4.42, P=0.042) and CC score of 2-3 (HR=2.31, 95%CI: 1.04-5.22, P=0.038) were the independent prognostic factors of reduced OS in colorectal cancer PM patients after CRS+HIPEC. Conclusions Rectal cancer PM patients demonstrate increased susceptibility to grade 3-4 complications and inferior survival outcomes compared to colon cancer PM patients after CRS+HIPEC, and the survival outcome is not ideal.

Key words: Colorectal cancer, Peritoneal metastasis, Cytoreductive surgery, Hyperthermic intraperitoneal chemotherapy, Prognosis