Prognostic Factors in Colorectal Cancer Patients with Synchronous Peritoneal Metastasis Undergoing Macroscopic Complete Resection: A Multicenter Prospective Observational Study.

Abstract

Objectives: Colorectal cancer (CRC) with synchronous peritoneal metastasis is considered to have a worse prognosis. Although macroscopic complete resection is associated with a favorable prognosis, the prognostic determinants in this population remain poorly characterized. Therefore, it is crucial to identify prognostic factors following macroscopic complete resection to determine optimal care strategies that improve patient outcomes and to predict prognosis.

Methods: In a multi-institute cohort study, we prospectively assessed clinicopathological factors that affect prognosis in 36 patients with CRC and synchronous peritoneal metastasis who underwent macroscopic complete resection.

Results: 26 of 36 patients (72%) developed recurrence during follow-up, with a median of 34 months. Peritoneum was the most common site of recurrence. In survival analysis, patients with low preoperative serum CA19-9 levels had a favorable overall survival compared with those with high preoperative serum CA19-9 levels (HR: 0.42, 95% CI: 0.15-1.21, P=0.044). Also, patients with right-sided CRC had more favorable overall survival than those with left-sided CRC (HR: 0.44, 95% CI: 0.18-1.06, P=0.047). Furthermore, right-sided CRC with low preoperative serum CA19-9 levels was associated with significantly better overall survival than those with high preoperative serum CA19-9 levels or left-sided CRC (HR: 0.17, 95% CI: 0.07-0.41, P<0.001).

Conclusions: In this prospective multi-institutional cohort of CRC patients with synchronous peritoneal metastasis undergoing macroscopic complete resection, recurrence was frequent, predominantly involving the peritoneum. Integrating tumor biology (sidedness) and serum biomarkers (CA19-9) may enhance prognostic stratification and guide individualized management strategies in this high-risk population.