Colic and rectal tumors with peritoneal metastases treated with cytoreductive surgery and HIPEC: One homogeneous condition or two different diseases? A systematic review and meta-analysis.

Colorectal cancer (CRC) peritoneal metastasis (PM) is one of the most important cause of cancer-related death in world. CRC PM is considered as a homogeneous disease without differentiating colonic or rectal origin. Aim of this study is to analyze survival of patients treated with cytoreductive surgery and HIPEC, according to the origin of PM. Literature search was performed to identify relevant articles. All meta-analysis were performed using mean difference and log of HR, when appropriate. The I2 statistic was used to determine the heterogeneity of included studies. Out of 349 selected records, 9 articles (1308 patients, 1153 colon PM and 155 rectal PM) have been included. OS and DFS is higher in patients affected by colon PM (OS mean difference: 24,49 months [95% CI: 14,70-34,28 months, p < 0,000001]; DFS mean difference: 7,75 months [95% CI: 1,37-14,13 months, p: 0,02]) and pooled Hazard Ratio for disease-related death in rectal PM is 1.62 [95% CI: 1,01-2,59, p: 0,05] compared to colon PM). Heterogeneity among selected studies is high in two subgroups and low in one (OS subgroup A I2: 98%, p < 0,000001; DFS subgroup I2: 91%, p < 0,000001; OS subgroup B I2: 25%, p: 0,26). Our analysis, with all the limitations related to included studies, suggests that peritoneal metastasis of rectal tumors treated with CRS and HIPEC have a worst prognosis of colon tumors PM. Larger studies are required to confirm those results and therefore we invite all Authors in considering also tumor localization when reporting data on CRC peritoneal metastasis treatment.