Background: The clinical course of metachronous peritoneal metastasis of colorectal origin is poorly understood. In this retrospective study, we aimed to elucidate survival and prognostic factors for metachronous peritoneal metastasis.
Methods: Patients with metachronous peritoneal metastasis after curative resection for stage I-III colon cancer were retrospectively reviewed, and the incidence and prognosis of metachronous peritoneal metastasis were investigated. Prognostic factors were identified by univariate and multivariate analyses.
Results: Among 1582 surgically resected stage I-III colon cancer patients, 65 developed metachronous peritoneal metastasis. The 5-year cumulative incidence rate was 4.5%, and the median survival after diagnosis of peritoneal metastasis was 29.6 months. None of the patients underwent peritonectomy or intraperitoneal chemotherapy. Independent prognostic factors included right colon cancer [hazard ratio (HR) 2.69, 95% confidence interval (CI) 1.26-5.64; p = 0.011], time to metachronous peritoneal metastasis of <1 year (HR 2.02, 95% CI 1.04-3.87; p = 0.040), Peritoneal Cancer Index (PCI) >10 (HR 3.68, 95% CI 1.37-8.99; p = 0.012), concurrent metastases (HR 4.09, 95% CI 2.02-8.23; p < 0.001), and peritoneal nodule resection (HR 0.31, 95% CI 0.13-0.65; p = 0.002).
Conclusions: A proportion of colon cancer patients with metachronous peritoneal metastasis may benefit from combined peritoneal nodule resection and systemic chemotherapy. Right colon cancer, early peritoneal metastasis, a high PCI, and concurrent metastases negatively affected prognosis in patients with metachronous peritoneal metastasis.