(PM P23) Rate of Peritoneal Carcinomatosis in Surgically-Resected Stage II and III Colon Cancer

Introduction: Incidence of peritoneal carcinomatosis (PC) after curative resection of stage II/III colon cancer varies widely. Although certain features are considered high-risk for PC, the impact of these features on PC incidence is unclear.

Methods: A retrospective analysis was performed on patients over 18 years old with surgically-resected stage II/III colonic adenocarcinoma treated at our institution from 2008-2018. Clinicopathologic, treatment and outcomes data were recorded. Patients with reported high-risk features (pT3N0-2 with mucinous/signet ring components, pT4, pN1c, perforation) were identified. The remaining stage II/III patients were used for comparison.

Results: Of 97 patients identified, 36/97 (37.1%) were stage II and 61/97 (62.9%) were stage III. Median follow-up time was 27 (1-146) months. Adjuvant systemic treatment was administered to 57/97 (58.8%) patients. Overall incidence of PC was 9/97 (9.3%) and the median time to PC was 20 (7-37) months. At time of PC identification, 6/9 (66.7%) were isolated PC, while 3/9 (33.3%) were PC with additional metastatic sites. The high-risk and comparison groups contained 61 and 36 patients, respectively. Incidence of PC was not significantly different between groups (high-risk 9.8% vs. comparison 8.3%, p=0.81). Median time to PC was also not significantly different (high-risk 23 (14-37) months vs. comparison 20 (7-36) months, p=0.74).

Conclusion: Overall PC incidence in patients with stage II/III colon cancer patients was 9.3%. Because PC incidence was not significantly higher in patients with previously reported high-risk features, future studies designed to evaluate PC in stage II/III colon cancer should include all patients regardless of high-risk features.