Phase II study of preoperative chemoradiotherapy (CRT) with irinotecan plus S-1 in locally advanced rectal cancer

Background and purpose: The aim of this study is to evaluate the efficacy and safety of preoperative radiation therapy combined with S-1 and irinotecan (SI) in LARC. Materials and methods: Patients were considered LARC if they had a T3/T4 lesion or node positive. Weekly doses of 40 mg/m² irinotecan were intravenously administered once per week during weeks 1-5 of radiotherapy. S-1 (70 mg/m²) was given from Monday to Friday in all weeks of radiotherapy. 3-D conformal radiotherapy was given at daily fractions of 1.8 Gy for 5 days for a total dose of 50.4 (45 + 5.4) Gy. Surgery was performed 4-6 weeks following the completion of chemoradiation. Results: Between June 2006 and November 2007, 43 pts were enrolled. The stage was: cT3 24 patients, cT4 6 patients; 28 patients were cN+. Forty-one patients completed the chemoradiation and 42 patients underwent operation: a low anterior resection was performed in 36 patients, a total colectomy in 1 patient, and an abdominal perineal resection in 5 patients. T downstaging was observed in 50%; 23 N+ patients became N- (55%). The complete pathological response was observed in 9 patients (21%). The 3-year locoregional failure rate, distant failure rate, disease-free survival, and overall survival were 9.5%, 18.6%, 72.1%, and 94.3%, respectively. Only three patients experienced G3 diarrhea; one had G3 sepsis and two had septic shock. Hematological toxicity (G3-G4) was observed in five patients. Conclusions: This study demonstrated the efficacy of preoperative CRT with S-1 and irinotecan with 21% of complete response. However, prompt recognition and management of infection is needed to use it in patients with locally advanced rectal cancer.