Linear Relationship of Peritoneal Cancer Index and Survival in Patients with Peritoneal Metastases from Colorectal Cancer

The peritoneal cancer index (PCI) is the main prognostic factor for establishing potentially resectable peritoneal metastases from colorectal cancer. Attempts have been made to set a PCI cutoff on which to base indications of complete cytoreductive surgery (CCRS) with hyperthermic intraperitoneal chemotherapy (HIPEC), but none have reached consensus. The aim of this study was to investigate the relation between the PCI and overall survival (OS). We included all consecutive patients homogeneously treated with CCRS and HIPEC between 2003 and 2012. The PCI was calculated at the end of the surgical procedure. The correlation between the PCI and OS was studied using statistical modeling from the simplest to the most complex methods (including linear, quadratic, cubic, and spline cubic). These models were compared by Akaike's information criteria (AIC). For the 173 treated patients, 5-year OS reached 41 %. The mean PCI was 10.2 (+/- 6.8). The linear model was the most appropriate to relate the PCI to OS as confirmed with the AIC scoring system. In multivariate analysis, the PCI was confirmed as being the most important prognostic factor (hazard ratio = 1.1 for each supplementary point, p < 0.0001). There is a perfect linear correlation between the PCI and OS, which precludes setting a unique PCI cutoff for CCRS + HIPEC. Overall, CCRS + HIPEC is generally indicated for PCI < 12 and contraindicated for PCI > 17. Between 12 and 17, other parameters have to be taken into account, such as the presence of extraperitoneal metastases, general performance status, and chemosensitivity.