• Shinya Morimoto, Mitsuo Shimada, Nobuhiro Kurita, Hirohiko Sato, Takashi Iwata, Masanori Nishioka, Kozo Yoshikawa, Tomohiko Miyatani, Hideya Kashihara, Chie Takasu, and Hitoshi Ikushima.
• Department of Surgery and Transplantation, Tokushima University Hospital, Tokushima, Japan. morimoto@clin.med.tokushima-u.ac.jp
• Hepato Gastroenterol. 2012 Jul 1;59(117):1428-32.

Background/AimsS-1 based chemoradiation is the recommended treatment for rectal cancer; however, the optimal scheduling and dosing are not yet established. A Phase I study was conducted to determine the maximum tolerated dose (MTD) of S-1 with radiotherapy (RT). Endpoints were the toxicity profile of this regimen and to determine the recommended dose (RD).MethodologyConformal RT was given using 4 fields at daily fractions of 2Gy on 5 days per week to a total dose of 40Gy. Concurrently S-1 was given twice daily throughout RT. Eligible patients had a newly diagnosed clinical stage T3-4 N0-2 M0 rectal adenocarcinoma located within 12cm of the anal verge suitable for curative resection. Surgery was performed 6 weeks from completion of preoperative chemoradiotherapy. The dose escalating from S-1 80mg/m2/day (Level 1) to 100mg/m2/day (Level 2).ResultsNine patients were valid for safety. In all patients, S-1 was administered. There was no dose-limiting toxicity (DLT) in patients treated at dose Level 1. Six patients were enrolled in the dose-escalation phase. At dose Level 2, two patients developed DLT and this was considered the MTD. Objective response according to RECIST were observed in 5 of 9 patients who had measurable disease (56%).ConclusionsThe RD of S-1 with concurrent RT was determined to be 80mg/m2/day. Preoperative RT combined with S-1 was feasible and well tolerated.

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