The Accuracy of the Surgical Peritoneal Cancer Index in Patients with Peritoneal Metastases of Colorectal Cancer.

Introduction: The peritoneal cancer index (PCI) is one of the most important prognostic factors in patients with peritoneal metastases from colorectal cancer undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). The PCI is determined during laparotomy by 2 experienced surgeons and plays a major role in the decision to proceed with CRS-HIPEC. The primary objective of this study was to determine the accuracy of the surgical PCI (sPCI) by comparing it with the PCI confirmed by the pathologist (pPCI).

Methods: All consecutive patients who underwent CRS-HIPEC for colorectal peritoneal metastases between February 2015 and June 2018 were identified. Relevant patient- and tumor-related characteristics were collected.

Results: In total, 119 patients were included, 60 males (50.4%). The median age was 64 (IQR 55-71). The median sPCI (sPCI = 11, IQR 6-16) was significantly higher than the median pPCI (pPCI = 8, IQR 3-13, p < 0.001). The total pPCI was lower than the total sPCI in 80 patients (67.2%). In 21 patients (17.6%), the sPCI was overestimated with ≥5 points. Small lesions are more likely to be negative. In patients that underwent resection of their primary tumor prior to CRS-HIPEC, the difference between the sPCI and pPCI was significantly larger (p < 0.05).

Conclusions: Surgical calculation of the PCI often results in overestimation. Far-reaching consequences are tied to the macroscopic evaluation of the sPCI, but this evaluation seems not very reliable.