Nonoperative Rectal Cancer Management With Short-Course Radiation Followed by Chemotherapy: A Nonrandomized Control Trial

Short-course radiation therapy (SCRT) and nonoperative management are emerging paradigms for rectal cancer treatment. This clinical trial is the first to evaluate SCRT followed by chemotherapy as a nonoperative treatment modality. Patients with nonmetastatic rectal adenocarcinoma were treated on the single-arm, Nonoperative Radiation Management of Adenocarcinoma of the Lower Rectum study of SCRT followed by chemotherapy. Patients received 25 Gy in 5 fractions to the pelvis followed by FOLFOX ×8 or CAPOX ×5 cycles. Patients with clinical complete response (cCR) underwent nonoperative surveillance. The primary end point was cCR at 1 year. Secondary end points included safety profile and anorectal function. From June 2016 to March 2019, 19 patients were treated (21% stage I, 32% stage II, and 47% stage III disease). At a median follow-up of 27.7 months for living patients, the 1-year cCR rate was 68%. Eighteen of 19 patients are alive without evidence of disease. Patients with cCR versus without had improved 2-year disease-free survival (93% vs 67%; P = .006), distant metastasis-free survival (100% vs 67%; P = .03), and overall survival (100% vs 67%; P = .03). Involved versus uninvolved circumferential resection margin on magnetic resonance imaging was associated with less initial cCR (40% vs 93%; P = .04). Anorectal function by Functional Assessment of Cancer Therapy-Colorectal cancer score at 1 year was not different than baseline. There were no severe late effects. Treatment with SCRT and chemotherapy resulted in high cCR rate, intact anorectal function, and no severe late effects. NCT02641691. Short-course radiation therapy results in higher pathologic complete response than long-course chemoradiation therapy in rectal adenocarcinoma. All definitive treatment experiences with nonoperative intent have used long-course chemoradiation. This prospective clinical trial of 20 patients is the first experience of nonoperative management with short-course radiation followed by chemotherapy. We observed a high clinical complete response rate with no severe late toxicity.