Reappraisal of Peritoneal Washing Cytology in 984 Patients with Pancreatic Ductal Adenocarcinoma Who Underwent Margin-Negative Resection

Objective The objective of the present study was to reappraise the clinical value of peritoneal washing cytology (CY) in 984 pancreatic ductal adenocarcinoma patients who underwent margin-negative resection. Methods In a 2001-2011 database from seven high-volume surgical institutions in Japan, 69 patients (7 %) had positive CY (CY+ group) indicative of M1 disease and 915 patients had negative CY (CY- group). Clinicopathological data and survival were compared between groups. Results Significant correlations between CY+ and high CA19-9 level, pancreatic body and tail cancer, lymph node metastasis, and a lower frequency of R0 resection were observed. Overall survival (OS) of CY+ patients was significantly worse than that of CY- patients (median survival time [MST], 16 vs. 25 months; 3-year OS rate, 6 vs. 37 %; p < 0.001). CY+ patients had a significantly higher rate of post-operative peritoneal carcinomatosis thanCY- patients (48 vs. 21 %; p < 0.001). Administration of adjuvant chemotherapy did not provide a favorable survival outcome to CY+ patients. The current study showed that patients with M1 disease had acceptable MST after margin-negative resection and a high incidence of peritoneal carcinomatosis within 3 years after surgery, resulting in decreased long-term survival. The development of a new strategy to control peritoneal carcinomatosis when surgical resection is performed in such patients is required.