Development of a Prognostic Nomogram for Patients with Peritoneally Metastasized Colorectal Cancer Treated with Cytoreductive Surgery and HIPEC.

ABSTRACT

BACKGROUND: With the introduction of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC), long-term survival can be achieved in selected patients with colorectal peritoneal metastases (PM). Patient selection and outcome may be improved significantly with a tool that adequately predicts survival in these patients. This study was designed to validate the peritoneal surface disease severity score (PSDSS) in patients with colorectal PM treated with CRS + HIPEC. If performance of the PSDSS was suboptimal (c < 0.7), we aimed to develop a new prognostic model. METHODS: Patients were included if they had colorectal PM and underwent CRS + HIPEC with intended complete cytoreduction in a Dutch tertiary hospital between 2007 and 2015. Statistical analyses were performed with R-software. RESULTS: A total of 200 patients underwent CRS + HIPEC. External validation of the PSDSS showed a Harrell's c statistic of 0.62. After analysis, four parameters appeared prognostically relevant factors for overall survival age, PCI score, locoregional lymph node status, and signet ring cell histology. The weighted relevance of these parameters was turned into a prognostic nomogram that we termed colorectal peritoneal metastases prognostic surgical score (COMPASS). The COMPASS differentiated well and showed a Harrell's c statistic of 0.72 with a calibration plot showing good agreement. CONCLUSIONS: This study externally validated the PSDSS and developed a new prognostic score, the COMPASS. This pre-cytoreduction nomogram was more accurate than PSDSS in predicting survival of patients undergoing CRS + HIPEC. It can be used as tool to assist in the decision about continuing cytoreduction and HIPEC and can provide valuable information in the follow-up period after CRS + HIPEC.