Background The clinical importance of intraoperative peritoneal cytology in patients with pancreatic cancer remains incompletely understood. Methods Peritoneal washing samples were collected from 411 consecutive patients with pancreatic ductal adenocarcinoma from 1996 to 2014. Of the 411 patients, 335 underwent macroscopically curative resection and 76 with noncurative factors did not undergo resection. We compared long-term outcomes between patients with positive cytology (cytology+) and those with negative cytology (cytology−) and investigated the importance of clinicopathologic factors. Results Of 335 patients with curative resection, 300 (89.6%) were cytology− and 35 (10.4%) were cytology+. The median overall survival of cytology+ patients was less than that of cytology− patients (16 vs 31 months, respectively; P < .0001). The median overall survival of cytology+ patients with noncurative factors was significantly worse than that of cytology+ patients with curative resection (6.9 vs 16.0 months, respectively; P = .0023). The median disease-free survival of cytology+ patients was less than that of cytology− patients (6.5 vs 16 months, respectively; P < .0001). In the multivariate analysis, cytology+ was an independent prognostic factor for overall survival and disease-free survival. Conclusion Cytology+ without noncurative factors was a predictive factor for a poor prognosis. Therefore, it is important to regard patients with pancreatic cancer characterized by cytology+ as a special group that may warrant more aggressive adjuvant therapy.
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