Should we exclude patients with peritoneal carcinosis of colorectal origin and high PCI from CRS + HIPEC?

: International guidelines exclude from surgery patients with peritoneal carcinosis of colorectal origin and a peritoneal cancer index (PCI) ≥ 16. This study aims to analyze the outcomes of patients with colorectal peritoneal carcinosis and PCI greater or equal to 16 treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) (CRS + HIPEC). We retrospectively performed a multicenter observational study involving three Italian institutions, namely the IRCCS Policlinico San Matteo in Pavia, the M. Bufalini Hospital in Cesena, and the ASST Papa Giovanni XXIII Hospital in Bergamo. The study included all patients undergoing CRS + HIPEC for peritoneal carcinosis from colorectal origin from November 2011 to June 2022. The study included 71 patients: 56 with PCI < 16 and 15 with PCI ≥ 16. Patients with higher PCI had longer operative times and a statistically significant higher rate of not complete cytoreduction, with a Completeness of Cytoreduction score (CC) 1 (microscopical disease) of 30.8% (p = 0.004). The 2-year OS was 81% for PCI < 16 and 37% for PCI ≥ 16 (p < 0.001). The 2-years DFS was 29% for PCI < 16 and 0% for PCI ≥ 16 (p < 0.001). The 2-year peritoneal DFS for patients with PCI < 16 was 48%, and for patients with PCI ≥ 16 was 57% (p = 0.783). CRS and HIPEC provide reasonable local disease control for patients with carcinosis of colorectal origin and PCI ≥ 16. Such results form the basis for new studies to reassess the exclusion of these patients, as set out in the current guidelines, from CRS and HIPEC. This therapy, combined with new therapeutical strategies, i.e., pressurized intraperitoneal aerosol chemotherapy (PIPAC), could offer reasonable local control of the disease, preventing local complications. As a result, it increases the patient's chances of receiving chemotherapy to improve the systemic control of the disease.