Real-world evidence for preoperative use of (chemo)radiotherapy with intensity modulation for locally advanced rectal cancer by the Colib French group

Abstract

Purpose: The acute toxicity of chemoradiotherapy can cause treatment interruptions and diminish patient quality of life. Recently, intensity-modulated radiotherapy has been shown to delineate treatment areas more precisely, thereby sparing unnecessary radiation exposure to organs at risk. However, the French national health authority does not currently recommend intensity-modulated radiotherapy for rectal cancer. This study aims to provide real-world data to evaluate the effectiveness of (chemo)radiotherapy with intensity modulation in the preoperative treatment of locally advanced rectal cancer.

Materials and methods: This retrospective study was conducted in a private practice setting in France. Patients included had confirmed, locally advanced rectal adenocarcinoma and had received neoadjuvant (chemo)radiotherapy with intensity modulation followed by surgery.

Results: A total of 700 patients underwent (chemo)radiotherapy with intensity modulation for a median duration of 6 weeks, most frequently using 45 to 50.4Gy. Thirty-seven patients had local disease progression, 98 experienced distant disease relapse, and 39 patients died during the follow-up period. Severe toxicity occurred in 5 % of patients (n=37), which was lower than the toxicity rates reported in previous studies with conformal radiotherapy. Small bowel V40 was identified as a predictive factor. Downstaging T (0.572, 95 % confidence interval [95 % CI]: 0.372-0.880, P<0.0110), downstaging N (0.522, 95 % CI: 0.332-0.820, P<0.0048), pathological complete response rate (0.4432, 95 % CI: 0.218-0.854, P<0.0158), and no abdominal surgery (0.541, 95 % CI: 0.360-0.812, P<0.0077) were found to be predictive for survival.

Conclusions: Neoadjuvant (chemo)radiotherapy with intensity modulation was found to reduce the incidence of acute gastrointestinal toxicity events compared to conformal radiotherapy, without compromising efficacy in patients with locally advanced rectal cancer.

Keywords: Cancer; Efficacité; Efficacy; IMRT; Localement évolué; Locally advanced rectal cancer; Preoperative treatment; Préopératoire; RCMI; Rectum.