S-1 plus gemcitabine chemotherapy followed by concurrent radiotherapy and maintenance therapy with S-1 for unresectable pancreatic cancer

AIM: To investigate the feasibility and efficacy of the combination of S-1 with gemcitabine followed by oral S-1 with concurrent radiotherapy (intensity modulated radiotherapy, IMRT) and maintenance therapy with S-1 for locally advanced pancreatic cancer.METHODS: Subjects selected in the study were patients who had unresectable and locally advanced pancreatic cancer without distant metastases, adequate organ and marrow functions, an Eastern Cooperative Oncology Group performance status of 0-1 and no prior anticancer therapy. Initially the subjects received two cycles of chemotherapy, oral administration of S-1 40 mg/m² twice daily from day 1 to day 14 of a 21-d cycle, with 30-min intravenous infusions of gemcitabine 1000 mg/m² on day 1 and day 8. Two weeks after the completion of chemotherapy, S-1 was administered orally with concurrent IMRT. Oral S-1 was administered at a dose of 80 mg/m² per day twice daily from day 1 to day 14 and from day 22 to day 35. Radiation was concurrently delivered at a dose of 50.4 Gy (1.8 Gy/d, 5 times per week, 28 fractions). One month after the completion of chemotherapy and radiotherapy, S-1 was administered orally at a dose of 80 mg/m² per day twice daily for 14 d, followed by a 14-d rest period. This cycle was repeated as maintenance therapy, until unacceptable toxicity occurred or the disease worsened. Thirty-two patients were involved in this study. The median follow-up was 15.6 mo (range: 8.6-32.3 mo).RESULTS: Thirty-two patients completed the scheduled course of chemotherapy, while 30 patients (93.8%) received chemoradiotherapy with two patients ceasing to continue with radiotherapy. The major toxic effects were nausea and leukopenia. There was no grade 4 toxicity or treatment-related death. According to the Response Evaluation Criteria in Solid Tumors criteria, the objective tumor response was partial response in 17 (53.1%) patients, stable disease in 9 (28.1%), and progressive disease in 6 (18.8%). The median overall survival and median progression-free survival were 15.2 mo and 9.3 mo, respectively. The survival rates at 1 year and 2 years were 75% and 34.4%, respectively.CONCLUSION: The combination of S-1 with gemcitabine followed by oral S-1 with IMRT and maintenance therapy with S-1 alone in patients with locally advanced pancreatic cancer may be considered a well-tolerated, promising treatment regimen.