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Published on: May 19, 2022
Preoperative radiotherapy combined with S-1 for advanced lower rectal cancer: phase I trial
Shinya Morimoto1, Mitsuo Shimada, Nobuhiro Kurita
1Department of Surgery and Transplantation, Tokushima University Hospital, Tokushima, Japan. morimoto@clin.med.tokushima-u.ac.jp
Background/Aims:
S-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).
Methodology:
Conformal 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).
Results:
Nine 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%).
Conclusions:
The 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.
