Cytoreductive surgery for synchronous and metachronous colorectal peritoneal dissemination: Japanese P classification and peritoneal cancer index

Aim The outcomes of cytoreductive surgery (CRS) for synchronous and metachronous colorectal peritoneal dissemination were investigated using the Japanese P classification and peritoneal cancer index (PCI). Methods CRS was performed in 111 cases of synchronous peritoneal dissemination and 115 cases of metachronous peritoneal dissemination. The P classification and PCI were determined at the time of laparotomy. Results In the synchronous dissemination group, the 5‐year overall survival rates after CRS in P1/P2 and P3 cases were 51% and 13%, respectively. Even for P3, 51% of the patients achieved macroscopic cytoreductive complete resection (CC‐0), with a 5‐year survival rate of 40%. When P3 cases were classified into PCI 0–9, 10–19, 20–29, and 30–39, CC‐0 was achieved in 93%, 70%, 6%, and 0% of the cases, respectively, and the 5‐year survival rate of PCI 0–9 was 41%. In the metachronous dissemination group, the 5‐year survival rates were 62% for PCI 0–9 and 22% for PCI 10–19; 5‐year survival was not observed in patients with a PCI ≥ 20. CC‐0 was significantly associated with the postoperative prognosis in both synchronous and metachronous peritoneal dissemination. Conclusion In cases of synchronous dissemination, CRS must be performed for P1 and P2 cases or those with a PCI