Incidence, prevalence and risk factors for peritoneal carcinomatosis from colorectal cancer

Background: This was a population-based cohort study to determine the incidence, prevalence and risk factors for peritoneal carcinomatosis (PC) from colorectal cancer. Methods: Prospectively collected data were obtained from the Regional Quality Registry. The Cox proportional hazards regression model was used for multivariable analysis of clinicopathological factors to determine independent predictors of PC. Results: All 11 124 patients with colorectal cancer in Stockholm County during 1995-2007 were included and followed until 2010. In total, 924 patients (8.3 per cent) had synchronous or metachronous PC. PC was the first and only localization of metastases in 535 patients (4.8 per cent). The prevalence of synchronous PC was 4.3 per cent (477 of 11 124). The cumulative incidence of metachronous PC was 4.2 per cent (447 of 10 646). Independent predictors for metachronous PC were colonic cancer (hazard ratio (HR) 1.77, 95 per cent confidence interval 1.31 to 2.39; P = 0.002 for right-sided colonic cancer), advanced tumour (T) status (HR 9.98, 3.10 to 32.11; P < 0.001 for T4), advanced node (N) status (HR 7.41, 4.78 to 11.51; P < 0.001 for N2 with fewer than 12 lymph nodes examined), emergency surgery (HR 2.11, 1.66 to 2.69; P < 0.001) and non-radical resection of the primary tumour (HR 2.75, 2.10 to 3.61; P < 0.001 for R2 resection). Patients aged > 70 years had a decreased risk of metachronous PC (HR 0.69, 0.55 to 0.87; P = 0.003). Conclusion: PC is common in patients with colorectal cancer and is associated with identifiable risk factors.