Optimal treatment strategy for patients with pancreatic cancer having positive peritoneal cytology: A nationwide multicenter retrospective cohort study supervised by the Japanese Society of Hepato-Biliary-Pancreatic Surgery.

Background: The aim of this study was to determine the optimal treatment for patients with pancreatic cancer (PaCa) having positive peritoneal cytology (PPC).

Methods: This multicenter retrospective study included patients with PPC treated at 78 high-volume centers between January 2012 and December 2020. Prognoses after resection (S-group) and initiation of nonsurgical treatment (N-group) were compared. Prognostic factors for survival in both groups were analyzed. Detailed characteristics of conversion surgery (CS) in the N-group were evaluated.

Results: In total, 568 enrolled patients were classified into an S-group (n = 445) or an N-group (n = 123). Median survival times (MSTs) were 19.0 months and 19.3 months, respectively, with no significant difference in prognosis (p = .845). The intervenable prognostic factors for survival were adjuvant treatment in the S-group (p < .001) and CS in the N-group (p < .001). Following CS, the MST was prolonged to 45.6 months, and peritoneal or liver recurrence decreased considerably. CS can be expected if PPC is diagnosed before neoadjuvant treatment and when combination treatment is initiated.

Conclusion: Surgical resection may not be beneficial for improving survival when PPC is evident. Chemotherapy aiming for CS may be the optimal treatment for such patients.