A Phase I Study of S-1-based Concurrent Chemoradiotherapy Followed by Gemcitabine and S-1 in Metastatic Pancreatic Adenocarcinoma

Background/Aim: Radiotherapy is not routinely used in metastatic pancreatic ductal adenocarcinoma (PDAC). We conducted a phase I study to investigate concurrent chemoradiotherapy (CCRT) followed by chemotherapy. Materials and Methods: S-1 was administered at 50-70 mg/m(2)/day with radiotherapy in 2.5-3.6 Gy/day for 10-12 fractions. After CCRT, gemcitabine (1,000 mg/m(2) on days 1 and 15) and S-1 (60-100 mg/day on days 1-7 and 15-21), were administered in a 4-week cycle. Results: After enrolling 10 patients, the study was terminated due to slow recruitment. Dose-limiting toxicities and maximum tolerated doses were not identified. Most patients experienced mild toxicities, including nausea, vomiting, and anorexia. One patient developed grade 3 infection. One patient achieved partial remission, while the remaining nine patients had stable disease, with a local disease control rate of 100% after CCRT. Conclusion: A short-course CCRT followed by chemotherapy was potentially feasible in patients with metastatic PDAC.