512P - The Prognostic Relevance of Histological Subtype in Patients with Peritoneal Carcinomatosis of Colorectal Cancer: a Nationwide Population-Based Study

Abstract

ABSTRACT Aim: With evolving treatment possibilities for patients with peritoneal carcinomatosis (PC) of colorectal cancer (CRC), adequate prognostication and patient selection for treatment becomes increasingly important. The prognostic relevance of commonly identified histological subtypes in patients with PC of CRC being adenocarcinoma (AC), mucinous adenocarcinoma (MC) and signet-ring cell carcinoma (SC) is currently unclear and was investigated in the current population-based study. Methods: This nationwide study involved 3551 patients diagnosed with synchronous PC from CRC between 2005-2011 in the Netherlands, as recorded in a nationwide registry. Kaplan-Meier analysis and log-rank testing were performed to estimate survival. Subsequently a Cox proportional hazard model was used to calculate hazard ratios for the risk of death. Results: The majority of the CRC patients was diagnosed with AC (n = 2465, 69%), whereas MC and SC were found in 836 (24%) and 250 (7%) patients respectively. SC was more frequently found in younger patients, advanced stage and poor differentiation grade. SC was associated with the highest risk of death, with a median survival of 6.8 months. For MC, median survival varied between 10 months in colon and 11 months in rectal cancer. The median survival in AC was respectively 7.1 months in colon cancer and 10.6 months in rectal cancer. Conclusions: Histological subtype is an important prognostic factor in patients with synchronous PC of CRC. This knowledge will aid clinicians in counseling of patients and clinical decision-making regarding possible treatment options. Disclosure: All authors have declared no conflicts of interest.