Gastrointestinal Cancer

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SU_2_2014 - The Efficacy and Tolerability of S-1 in the Treatment of Preoperative Chemoradiotherapy for Locally Advanced Rectal Cancer.

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

The Efficacy and Tolerability of S-1 in the Treatment of Preoperative Chemoradiotherapy for Locally Advanced Rectal Cancer.
N. Imano1, I. Nishibuchi1, Y. Takeuchi1, I. Takahashi1, K. Miki2, A. Saito3, T. Kimura1, Y. Murakami1, and Y. Nagata4; 1Department of Radiation Oncology, Hiroshima University, Hiroshima, Japan, 2Department of Radiation Oncology, Hiroshima University Hospital, Hiroshima, Japan, 3Washington University, St. Louis, MO, 4Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan

Purpose/Objective(s): Preoperative chemoradiotherapy (CRT) is a standard treatment for locally advanced rectal cancer (LARC). Capecitabine or 5-FU has been adopted as a standard concurrent chemotherapy regimen. S-1, a prodrug of 5-FU, is one of the candidates for chemotherapy regimen in Japan; however, there are few reports on the treatment outcome of preoperative CRT with S-1 alone for LARC. The purpose of this study is to assess the efficacy and tolerability of S-1 in the treatment of preoperative CRT for LARC.

Materials/Methods: We retrospectively evaluated 40 LARC patients who underwent preoperative CRT with S-1 alone in our institution between 2005 and 2016. Patients who had distant metastasis were excluded. The median age was 62 years (range, 30–85 years). The clinical tumor stage was cT2 in 5 (all had lymph node metastasis), cT3 in 20 patients, cT4a in 6 and cT4b in 9; 24 patients had clinical evidence of lymph node metastasis; cStage II in 10 patients and cStage III in 30 patients. In principle, S-1 with a dose of 80 mg/m2/day was orally administered twice a day on days 1–14 and 22–35 concomitantly with radiotherapy (RT). A total dose of 45 -50.4 Gy was delivered in 25-28 fractions over 5 weeks (median: 50.4 Gy). Surgical resection was scheduled 6–8 weeks after the completion of CRT (median: 55 days). The Kaplan–Meier method was used to generate survival curves.

Results: The completion rate of oral S-1 administration was 90% (36/40). In four patients S-1 was stopped due to acute toxicities (Grade 3 neutropenia in two, Grade 3 diarrhea in one, Grade 2 anorexia in one). The completion rate of planned RT was 97.5% (39/40). RT was terminated in one patients at a dose of 46.8 Gy due to Grade 3 diarrhea. Interruption of CRT was required in two patients because of abdominal abscess and appendicitis, respectively. A pathological complete response (pCR) was observed in 5 patients (12.5%), Pathological downstaging was observed in 30 patients (75%). R0 resection was achieved in all patients. With a median follow-up time of 44 months, the 3-year overall survival and progression-free survival rates were 90% and 64%, respectively. The 3-year local control rate was 94%. Six patients (15%) had Grade 3 acute toxicities for CRT, including diarrhea in two, neutropenia in two, anal mucositis in one, anemia in one patient.

Conclusion: Preoperative CRT with S-1 alone showed good completion rate and low incidence of severe acute toxicities. In addition, favorable down staging, local control and overall survival rates were obtained. S-1 alone can be an effective and safe treatment option in preoperative CRT for LARC.

Author Disclosure: N. Imano: Employee; Hiroshima university. I. Nishibuchi: None. Y. Takeuchi: None. I. Takahashi: None. K. Miki: None. A. Saito: None. T. Kimura: None.

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