Phase I study of oral fluoropyrimidine anticancer agent (S-1) with concurrent external-beam radiotherapy for unresectable pancreatic cancer
4109 Background: S-1 is an oral fluorouracil anticancer agent that was recently reported to demonstrate a response rate of 21% in 19 patients with advanced pancreatic cancer. Concurrent external-beam radiotherapy (EBRT) and 5-FU has been generally accepted as the standard treatment for locally advanced pancreatic cancer. However, there are no published data regarding the efficacy of combination therapy of S-1 and radiation in patients with pancreatic cancer. Our purpose of this study was to evaluate the safety of S-1 combined with EBRT and determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of S-1 in patients with locally advanced and unresectable pancreatic cancer. Methods: Eligible patients had UICC stage III or IV pancreatic cancer (either advanced unresectable or metastatic), adequate organ function, and no anticancer therapy in the preceding 4 weeks. S-1 was given orally at a dose of 60 mg/m2/day or 80 mg/m2/day in two divided doses after breakfast and supper. External-beam radiotherapy was delivered using a conformal technique in fraction of 1.25 Gy X 2/day, 5 days per week, totaling 50 Gy/40 fraction for 4weeks. S-1 at a dose of 60 mg/m2/day was given on days 1–7 and 15–21 in level 1, on days 1–14 in level 2, on days 1–21 in level 3a, respectively. S-1 at a dose of 80 mg/m2/day was given on days 1–21 in level 3b and on days 1–28 in level 4. DLT was defined as NCI-CTC grade 3/4 toxicity. Results: 18 patients were entered in this phase I trial: level 1 (4 patients), level 2 (5 patients), level 3a (3 patients), level 3b (3 patients), level 4 (3 patients). There were 1 of 5 patients with DLT in level 2: grade 3 vomiting. There were no DLT in levels 1, 3a, and 3b, respectively. Two of 3 patients in level 4 showed DLT: one patient developed grade 3 neutropenia and another patient developed grade 3 diarrhea. Clinical effects by CT scan included one PR, 15 SD and 2 PD. Reduced CA19–9 level less than a half of that at starting time was observed in 6 of 18 patients. Conclusions: S-1 at a dose of 80 mg/m2/day given on days 1–21 is safe and may be recommended for phase II study in patients with locally advanced and unresectable pancreatic cancer. This regimen appears to be a promising and well-tolerated approach with consideration of application to outpatients. No significant financial relationships to disclose.