Sequential boost in neoadjuvant irradiation for T3N0-1 rectal cancer: Long-term results from a single-center experience

Abstract

Purpose: To evaluate the influence of radiation dose on tumor regression grade (TRG) and sphincter preservation rate in a series of cT3N0-1 rectal cancer patients treated with neoadjuvant chemoradiotherapy (CT-RT) with or without a sequential radiation boost. Materials and methods: Between May 2002 and September 2013, 116 cases were eligible for retrospective evaluation. Radiotherapy was delivered for a total dose of 45 Gy (no boost arm) or 50.4 Gy (boost arm). TRG was evaluated with the Dworak scale. Results: Median follow-up was 62 months (range, 12-138 months). The 5-year overall survival and local control rates were 72% and 93%, respectively. Fifty-five patients (47%) were treated with a sequential radiation boost and 61 (53%) without a boost. Eighty patients (72%) presented T3N0 disease and 32 (28%) T3N1 disease. Concomitant capecitabine was administered in 92 cases (79%) and intravenous 5-fluorouracil in 24 cases (21%). Sphincter preservation was performed in 82% of patients in the boost arm and 66% in the no-boost arm. A higher TRG was related to a longer interval between neoadjuvant treatment and surgery (p<0.001). The probability of a TRG ≥2 was 2.5 times higher in the boost arm. A gain in local control, estimated at 4% during the first 3 years after CT-RT, favored the boost arm. Conclusions: The long-term results from our single-center experience confirm literature data on the role of a sequential boost in tumor response after neoadjuvant CT-RT in a series of cT3N0-1 rectal cancer patients.