Beyond total PCI thresholds: Limitations of the surgical peritoneal cancer index in decision-making for cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

The Peritoneal Cancer Index (PCI) is widely used to quantify disease extent and guide therapeutic decisions for cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) across multiple primary tumors. While PCI is a validated prognostic indicator, the use of a single total surgical PCI threshold as a determinant of eligibility for CRS-HIPEC presents significant conceptual and practical limitations. Surgical PCI calculation is subject to inter-surgeon variability, particularly at anatomical region boundaries, where lesion allocation may alter the total score sufficiently to influence treatment decisions. In addition, surgical PCI frequently overestimates disease extent compared with pathological PCI, while laparoscopic assessment may underestimate peritoneal involvement. Increasing evidence indicates that the anatomical distribution of peritoneal metastases, particularly involvement of critical regions such as the hepatoduodenal ligament, small bowel, and mesentery, is more predictive of resectability, morbidity, and oncologic outcome than aggregate PCI alone. Furthermore, the prognostic significance of PCI varies according to primary tumor biology, challenging the applicability of universal threshold values. These considerations suggest that total PCI should not be used in isolation to contraindicate CRS-HIPEC. Decision-making frameworks should instead emphasize regional disease distribution, technical resectability, and tumor-specific behavior to optimize patient selection.