Prognostic Significance of Peritoneal Metastasis in Stage IV Colorectal Cancer Patients With R0 Resection: A Multicenter, Retrospective Study

BACKGROUND: Stage IV colorectal cancer encompasses various clinical conditions. The differences in prognosis after surgery between different metastatic organs have not been fully investigated. OBJECTIVE: This study aimed to assess prognostic significance in peritoneal metastasis in R0 resected stage IV colorectal cancer. DESIGN: We conducted a multicenter retrospective study of patients with R0 resected stage IV colorectal cancer; they were categorized into 3 groups according to the number and location of metastatic organs, including single-organ metastasis in the peritoneum, single-organ metastasis at sites except the peritoneum, and multiple-organ metastases. SETTINGS: This study used data accumulated by the Japanese Study Group for Postoperative Follow-Up of Colorectal Cancer. PATIENTS: A total of 1133 patients with R0 resected stage IV colorectal cancer were registered retrospectively between 1997 and 2007 in 20 referral hospitals. MAIN OUTCOME MEASURES: Cancer-specific survival rates between the groups were measured. RESULTS: The median cancer-specific survival of the single-organ metastasis in the peritoneum group was considerably shorter than that of the single-organ metastasis at a site other than the peritoneum group and was almost comparable to that of the multiple-organ metastases group (3.41 years, 6.20 years, and 2.99 years). In a multivariate analysis of cancer-specific survival, peritoneal dissemination was confirmed as an independent prognostic factor of survival. The median postrecurrence survival of single-organ metastasis in the peritoneum group was considerably shorter than that of the single-organ metastasis at a site other than the peritoneum group. Approximately half of the patients who experienced recurrence of single-organ metastasis in the peritoneum experienced peritoneal recurrence. LIMITATIONS: This was a retrospective, population-based study that requires a prospective design to validate its conclusions. CONCLUSIONS: Peritoneal metastasis of colorectal cancer frequently recurred in the peritoneum even after R0 resection. The cancer-specific survival of the single-organ metastasis in the peritoneum group was as poor as that of the multiple-organ metastases group. See Video Abstract at http://ift.tt/2gXPyeF .

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