Acute Toxicity and Tumor Response in Locally Advanced Rectal Cancer After Preoperative Chemoradiation Therapy With Shortening of the Overall Treatment Time Using Intensity-Modulated Radiation Therapy With Simultaneous Integrated Boost: A Phase 2 Trial.

Abstract

This phase 2 study investigated the efficacy and safety of preoperative intensity modulated radiation therapy with a simultaneous integrated boost (IMRT-SIB) without dose escalation, concomitant with standard capecitabine chemotherapy in locally advanced rectal cancer. Between January 2014 and March 2015, 51 patients with operable stage II-III rectal adenocarcinoma received preoperative IMRT with pelvic dose of 41.8 Gy and simultaneously delivered 46.2 Gy to T2/3 and 48.4 Gy to T4 tumor in 22 fractions, concomitant with capecitabine, 825 mg/m²/12 hours, including weekends. The primary endpoint was pathologic complete response (pCR). Fifty patients completed preoperative treatment according to the protocol, and 47 underwent surgical resection. The sphincter preservation rate for the low rectal tumors was 62%, and the resection margins were free in all but 1 patient. Decrease in tumor and nodal stage was observed in 32 (68%) and 39 (83%) patients, respectively, with pCR achieved in 12 (25.5%) patients. There were only 2 G ≥ 3 acute toxicities, with infectious enterocolitis in 1 patient and dermatitis over the sacral area caused by the bolus effect of the treatment table in the second patient. Preoperative IMRT-SIB without dose escalation is well tolerated, with a low acute toxicity profile, and can achieve a high rate of pCR and downstaging.