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Dig Surg. 2016;33(1):66-73. doi: 10.1159/000442027. Epub 2015 Dec 1.

New Staging System for Colorectal Cancer Patients with Synchronous Peritoneal Metastasis in Accordance with the Japanese Classification of Colorectal Carcinoma: A Multi-Institutional Study.

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Department of Surgery, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.



Peritoneal metastasis of colorectal cancer (CRC) is often discovered during initial surgery. The aim of this study is to propose a new staging system that could be used to help determine the management of CRC patients.


We evaluated a total of 766 Stage IV CRC patients with synchronous peritoneal metastasis. According to the Japanese classification, we divided the peritoneal metastasis into P1, P2, and P3. We distinguished distant metastasis from liver metastasis and peritoneal metastasis. According to the Cox proportional hazard model, we constructed a new staging group.


According to a comparison of the R2 statistics, the combination of liver metastasis and peritoneal metastasis was selected as the final variables. Next, we defined P1H(-) as Grade A, P2H(-) as Grade B, and other groups as Grade C. Our proposed new stage (Akaike Information Criteria [AIC] 7,338.82; concordance index [c-index] 0.644; R2 0.123) could thus divide the patients into different prognostic groups more clearly than the current Japanese classification (AIC 7,373.89; c-index 0.619; R2 0.097).


Our proposed new staging system is very simple and easy for general surgeons to follow. This system is useful for determining the appropriate operative strategy for CRC patients with peritoneal metastasis and for estimating the patients' prognosis.

[Indexed for MEDLINE]

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