Background: The significance of surgical resection in pancreatic ductal adenocarcinoma (PDAC) with positive peritoneal cytology (PPC) is controversial. This study aimed to evaluate whether preceding chemotherapy could be beneficial for patients with PDAC with PPC. Methods: Between 2017 and 2019, 34 consecutive PDAC patients diagnosed with PPC without distant metastasis were retrospectively reviewed. Twenty-three patients did not receive neoadjuvant treatment (NAT) and 11 received NAT. All patients received systemic chemotherapy after PPC was confirmed, and they underwent surgical resection if PPC turned negative. The treatment course, ratio of conversion surgery (CS), and prognosis were evaluated. Moreover, the prognosis of PPC patients who underwent up-front surgery without NAT between 2003 and 2016 was analyzed as a comparative cohort. Results: The median survival time (MST) of the patients without NAT was 31.4 months. CS was performed in 52.2% of the patients. Patients who underwent CS had better prognoses than those who did not undergo CS (p = 0.005). The CS rate was significantly higher in resectable PDAC (78.5%) than in borderline/unresectable PDAC (11.1%) (p = 0.002). The prognosis of patients with resectable PDAC was improved with preceding chemotherapy compared with up-front surgery (MST 13.0 months; p = 0.016). After NAT, the CS rate was low (27.3%), and the MST was only 14.1 months. Conclusions: As an initial treatment for PDAC patients with PPC, chemotherapy may lead to a favorable prognosis. Especially, resectable PDAC is associated with a greater chance of improved prognosis. Future studies are required to ascertain whether up-front surgery or preceding chemotherapy should be performed for these patients.
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