(PM P12) Impact of Histology on Survival in Colon Cancer with Peritoneal Carcinomatosis: Does it really matter?

Background Peritoneal carcinomatosis (PC) is associated with a poor prognosis in patients with colon adenocarcinoma (CC). Mucinous adenocarcinoma is associated with PC and has worse outcomes when compared to non-mucinous adenocarcinomas. We sought to investigate the relationship of histologic subtype and overall survival (OS) in CC patients with PC. Methods The 2004-2015 National Cancer Database (NCDB) was queried for cases of CC with PC. Trends in treatment and survival outcomes were examined. Factors affecting OS were assessed with Kaplan-Meier and Cox regression analysis. Results Of 781,292 CC cases, 23,735 patients (3%) with PC were identified [median age 69 years, 49.5% male]. Most cancers were non-mucinous (87.2%), with 10.5% mucinous and 2.3% signet ring cell adenocarcinoma. The majority of cancers were low grade and right sided. The median OS was 37.4 months, with an OS of 38.3, 33.6, and 19.9 months for non-mucinous, mucinous, and signet ring cell subtypes, respectively. On multivariate analysis, increasing age, public or no insurance, high grade histology, R1 or R2 resection, and KRAS positivity were associated with worse outcomes while left sided tumors and receipt of chemotherapy conferred a survival benefit (p<0.01). Histologic subtype was not associated with OS in patients with PC (p=0.895). Conclusions In CC patients with PC, histologic subtype does not impact OS. Right sided and KRAS positive tumors with PC demonstrate worse OS regardless of histology, while patients with R0 resection and those receiving chemotherapy have a survival benefit. Consideration for aggressive surgical resection and multimodal therapy should be made when possible.