Prognostic significance of tumour regression grade after neoadjuvant chemoradiotherapy for a cohort of patients with locally advanced rectal cancer: an 8-year retrospective single-institutional study.

Aim Locally advanced rectal cancer (LARC) is frequently treated with neoadjuvant chemoradiotherapy (NACRT) to reduce the risk of local recurrence and improve survival. Tumour response to NACRT is variable and may influence the prognosis after subsequent surgery. This study compared the prognostic values of tumour regression grade (TRG) and neoadjuvant pathologic (ypTNM) downstaging in stage II and III rectal cancer patients treated with NACRT followed by curative surgery. Method This study included 185 LARC patients treated with long-course radiotherapy (45 Gy in 25 fractions) plus 5-fluorouracil over 5 weeks between 2005 and 2013. We used multivariate analysis to assess the relationship of Dworak's five-tier tumour regression grade (TRG), ypTNM stage, and ypTNM downstaging with clinicopathologic factors, 5-year disease free survival (DFS), and 5-year overall survival (OS). Results Total regression (TRG4), good regression (TRG3), moderate regression (TRG2), minor regression (TRG1), and no regression (TRG0) were seen in 38 (20.6%), 65 (35.2%), 43 (23.2%), 28 (15.1%), and 11 (5.9%) patients, respectively. TNM downstaging following NACRT occurred in 109 (58.9%) patients. The 5-year DFS rates after NACRT for TRG0, TRG1, TRG2, TRG3, and TRG4 were 0%, 58.5%, 66.4%, 80.4%, and 82.6%, respectively (P < 0.001). The ypTNM stage correlated with 5-year DFS (P = 0.004) but not 5-year OS (P = 0.075). Multivariate analysis demonstrated that TRG related to both DFS and OS (P < 0.001). Conclusion TRG measured on a five-tier system was better than ypTNM stage for predicting outcome in LARC patients treated with NACRT and surgery. This article is protected by copyright. All rights reserved.