Neoadjuvant chemoradiotherapy delivered with helical tomotherapy under daily image guidance for rectal cancer patients: efficacy and safety in a large, multi-institutional series.

Helical tomotherapy (HT) has been recently introduced in the neoadjuvant treatment of locally advanced rectal cancer. Aim of this study is to report the toxicity and local control rates of a large series of locally advanced rectal cancer patients treated with neoadjuvant chemotherapy and HT under daily image guidance followed by surgery. Data from 117 locally advanced rectal cancer patients treated at two Swiss Radiotherapy departments were collected and analyzed. Radiotherapy consisted of 45 Gy (1.8 Gy/fraction, 5 fractions/week delivered in 5 weeks) to the regional pelvic lymph nodes. Seventy patients also received a simultaneous integrated boost (SIB) up to 50 Gy to the tumor and involved nodes (2 Gy/fraction, 5 fractions/week delivered in 5 weeks). Chemotherapy consisted of capecitabine 825 mg/m <sup>2</sup> , twice daily, during the irradiation days. After a median interval of 59 days [95% confidence interval (CI) 53-65 days), all patients underwent surgery. Median follow-up was 45 months (range 4-90 months). The overall rate of acute grade 2-4 toxicity was 18.8% (n = 22). Four patients (3.4%) presented a grade 3 dermatitis (n = 1) or diarrhea (n = 3), and 1 (0.8%) demonstrated grade 4 rectal toxicity. No patients presented with grade ≥ 3 hematologic toxicity. Six patients (5.1%) had late grade 3 gastrointestinal toxicity. The 4-year local control rate was 88.4% (95% CI 87.5-88.5%). Neoadjuvant chemoradiotherapy delivered with HT under daily image guidance is well tolerated and shows a high 4-year local control rates