Findings in magnetic resonance imaging for restaging locally advanced rectal cancer

Abstract

Abstract Purpose We aimed to assess the prognostic value of restaging magnetic resonance imaging (MRI) in rectal cancer after neoadjuvant therapy and compare long-course chemoradiotherapy (LC-CRT) to short-course radiotherapy with delayed surgery (SCRT-delay). Methods This retrospective study included 267 patients with locally advanced rectal cancer (LARC) operated on between January 2016 and April 2019, all of whom received either LC-CRT or SCRT-delay in the neoadjuvant setting. The primary outcomes were overall survival (OS) and cancer-specific survival (CSS) based on radiological response assessed using the magnetic resonance tumor regression grade (mrTRG). Results In the LC-CRT group, cumulative 1-, 3-, and 5-year OS rates were 94.8%, 86.4%, and 79.0%, while in the SCRT-delay group, they were 83.3%, 68.9%, and 68.9% (P = 0.017). For CSS in the LC-CRT group, cumulative rates were 96.9%, 90.3%, and 85.0%, and in the SCRT-delay group, they were 88.6%, 81.4%, and 81.4% (P = 0.222). There were no significant differences in total histological response rates or local recurrence rates between the treatment groups. The good and moderate response group (mrTRG 1–3) had significantly better cumulative 1-, 3-, and 5-year OS and CSS compared to the poorer response group (mrTRG 4–5) (P = 0.023 for OS and P = 0.048 for CSS). Conclusion Unfavorable MRI response is a sign of poor prognosis in LARC. SCRT-delay is comparable to LC-CRT concerning the oncological outcome.