Nab-paclitaxel plus S-1 with or without PD-1 inhibitor in pancreatic ductal adenocarcinoma with only hepatic metastases: a retrospective cohort study.

PURPOSE The evidence regarding programmed cell death 1 (PD-1) inhibitors on pancreatic ductal adenocarcinoma (PDAC) with metastases remains controversial. This study aimed to assess the efficacy and safety of Nab-paclitaxel plus S1 (NPS) with or without Sintilimab, a PD-1 inhibitor, in patients with PDAC with only hepatic metastases (mPDAC). METHODS Untreated mPDAC patients who received NPS with (the combination group) or without Sintilimab (the NPS group) were retrospectively studied. Surgery was considered when the pancreatic tumor became resectable or borderline resectable on radiological examinations, and with complete metabolic response of liver metastases. RESULTS Between October 2017 and February 2020, 32 patients were in the combination group and 34 patients in the NPS group. Successful salvage resection was achieved in 17 (25.8%) patients after tumor-downstaging (combination 12 vs. NPS 5, P = 0.03). The median overall survival (OS) was 16.8 months in the combination group and 10.0 months in the NPS group (P = 0.002). Remarkable OS benefit was observed in patients with decline in CA19-9 of ≥ 50% (16.0 vs. 6.5, P = 0.003), reduction in 18F-fluorodeoxyglucose uptake of primary tumor of ≥ 50% (16.5 vs. 10.0, P < 0. 001) and after salvage resection (20.1 vs. 11.0, P < 0. 001). No significant difference in Grade 3 or higher adverse events were seen between the two groups (40.6% vs. 32.4%, P = 0.49). CONCLUSIONS Despite the inherent biases of this retrospective study, the addition of Sintilimab significantly improved salvage resection rates and OS compared with the NPS regimen and had a favorable safety profile in treatment naive mPDAC patients.