Long-Term Outcomes After R0 Resection of Synchronous Peritoneal Metastasis from Colorectal Cancer Without Cytoreductive Surgery or Hyperthermic Intraperitoneal Chemotherapy.

BACKGROUND: The National Comprehensive Cancer Network (NCCN) guidelines for colon cancer recently added the following footnote regarding the therapeutic strategy for peritoneal metastases: "If R0 resection can be achieved, surgical resection of isolated peritoneal disease may be considered at experienced centers." This study investigated the efficacy of R0 resection of peritoneal metastasis from colorectal cancer without cytoreductive surgery or hyperthermic intraperitoneal chemotherapy (HIPEC).

METHODS: This retrospective cohort study was conducted at a single-institution tertiary care cancer center. Among 496 consecutive M1c colorectal cancer patients, R0 resection was achieved for 94 patients (19%). The subjects were 78 consecutive patients with colorectal cancer and simultaneous peritoneal metastasis but no other distant metastases who underwent R0 resection at the National Cancer Center Hospital from 1971 to 2016 (16% of all M1c patients). Overall survival (OS) was investigated, and clinicopathologic variables were analyzed for prognostic significance.

RESULTS: No perioperative mortality was noted. The 3-year OS rate was 45%, and the 5-year OS rate was 28.7%. The median survival time was 33.4 months. Notably, 17 patients survived for more than 5 years, and 9 of these patients did not receive any chemotherapy. Multivariate analysis showed cancer location in the colon and harvesting of 12 or more lymph nodes to be independent factors associated with a better prognosis.

CONCLUSIONS: From the perspective of long-term outcomes and no perioperative mortality, R0 resection of peritoneal metastasis from colorectal cancer, without complete peritonectomy or HIPEC, appeared to be an acceptable therapeutic option for some patients with peritoneal metastasis.