Prognostic importance of peritoneal washing cytology in patients with otherwise resectable pancreatic ductal adenocarcinoma who underwent pancreatectomy: A nationwide, cancer registry–based study from the Japan Pancreas Society

Background: The importance of peritoneal washing cytology status both as a sign of irresectability and as a prognostic factor for pancreatic ductal adenocarcinoma remains controversial. The purpose of this nationwide, cancer registry–based study was to clarify the clinical implications of operative resection in patients who had positive cytology status. Methods: Clinical data from 1,970 patients who underwent tumor resection were collected from the Pancreatic Cancer Registry in Japan. Clinicopathologic factors and overall survival curves were analyzed, and multivariate Cox proportional hazard models were evaluated. Results: Among the 1,970 patients analyzed, positive cytology status was found in 106 patients and negative cytology status was found in 1,864 patients. The positive cytology status group had a greater frequency of pancreatic body and tail cancer and greater preoperative serum carbohydrate antigen 19-9 levels than the negative cytology status group (P <.001 each). The ratio of peritoneal recurrence tended to be greater in the positive cytology status group (14% vs 43%; P <.001). Overall median survival times were less in the positive cytology status group (17.5 months vs 29.4 months; P <.001). The 5-year survival rates were 13.7% and 31.1% in the positive cytology status and negative cytology status groups, respectively. Multivariate analysis of positive cytology status patients revealed that adjuvant chemotherapy was an independent prognostic factor. Conclusion: Positive cytology status was an adverse prognostic factor in patients who underwent resection for pancreatic ductal adenocarcinoma but did not preclude attempted curative resection. Curative resection followed by adjuvant chemotherapy may contribute to long-term prognosis in patients with positive cytology status.