Ninety percent of the adverse outcomes occur in 10% of patients: can we identify the populations at high risk of developing peritoneal metastases after curative surgery for colorectal cancer?

Background: Peritoneal metastases (PM) occur in 3.4-6.3% after curative surgery for non-metastatic colorectal cancer. Systematic 2nd look surgery helps overcoming the diagnostic problem but can be only proposed to selected patients. The aim of this study was to update the knowledge on risk factors of developing PM after curative surgery for colorectal cancer.Methods: A systematic review of the literature published between 2011 and 2016 was made, searching for all clinical studies reporting the incidence of recurrent PM after curative surgery for colorectal cancer and factors associated with the primary tumour that were likely to influence this recurrence rate.Results: Seven new clinical studies were considered informative for risk factors and added to the 16 reviewed in 2013. Even if the level of evidence was low, data suggested rates of recurrent PM at 1year between 54% and 71% after completely resected synchronous PM, between 62% and 71% after resection of isolated synchronous ovarian metastases, of 27% after surgery for a perforated primary tumour, of 16% after surgery for a pT4 tumour, and between 11% and 36% after surgery for a mucinous histological subtype. No new risk factor was identified.Conclusions: Evidence regarding the incidence of recurrent PM after curative surgery for colorectal cancer is poor. Situations at higher risk of recurrent PM are synchronous PM, synchronous isolated ovarian metastases, perforated primary tumour with serosa invasion and mucinous histological subtype.