Phase II study of preoperative helical tomotherapy with a simultaneous integrated boost for rectal cancer.

Abstract

Listen

Translate article

e14014 Background: Preoperative chemoradiotherapy is standard of care for locally advanced rectal cancer. However, adding concomitant chemotherapy to preoperative radiotherapy does not improve survival or the incidence of distant metastasis, and is associated with considerable grade 3+ toxic effects. The aim of this study is to explore the efficacy and toxicity profile of helical tomotherapy in the preoperative treatment of rectal cancer. Methods: This interim analysis reports the first 106 patients. A dose of 46 Gy, in daily fractions of 2 Gy, was delivered to the presacral space and the perineum if an abdominoperineal resection was deemed necessary. No concomitant chemotherapy was administered, but the dose of radiation was increased by a simultaneous integrated boost to 55.2 Gy, when the circumferential resection margin (CRM) was less than 2 mm. The response was determined by measuring the metabolic tumor volume prior to and five weeks after the end of radiotherapy by FDG-PET. Results: 54 patients presented with a T2 or good T3 tumor (CRM ≥ 2 mm) and entered the no boost group, 52 patients presented with a bad T3 (CRM < 2 mm) or T4 tumor on MRI and entered the boost group. One patient, in the no-boost group, developed grade 3 enteritis. No other grade 3+ acute toxicities were observed. 16, 12, 28 and 1 patient developed acute grade 2 gastrointestinal, urinary, dermatologic and gynecologic toxic effects respectively. The mean decrease in metabolic volume was 61 ± 30% in the no boost group, compared to 76 ± 27% in the boost group (p = 0.04). With a median follow-up of 25 months, 1 locoregional relapse was observed. Conclusions: Helical tomotherapy reduces acute toxicity in preoperative radiotherapy of rectal cancer. A simultaneous integrated radiation boost increases the metabolic response, without excessive toxicity. A multicentric randomized noninferiority multicenter trial that compares this approach to preoperative chemoradiotherapy is being initiated. No significant financial relationships to disclose.