Impact of Microscopically Positive (≤1 mm) Distal Margins on Disease Recurrence in Rectal Cancer Treated by Neoadjuvant Chemoradiotherapy

Abstract

The adequate distal resection margin is still controversial in rectal cancer treated by neoadjuvant chemoradiotherapy (nCRT). The aim of this study was to assess the impact of a distal margin of ≤1 mm on locoregional recurrence-free survival (LRRFS). Among 255 patients treated with nCRT and surgery at the National Cancer Institute of Milan, 83 (32.5%) had a distal margin of ≤1 mm and 172 (67.5%) had a distal margin of >1 mm. Survival analyses were performed to assess the impact of distal margin on 5-year LRRFS, as well as Cox survival analysis. The role of distal margin on survival was analyzed according to different tumor regression grades (TRGs). The overall 5-year LRRFS rate was 77.6% with a distal margin of ≤1 mm vs. 88.3% with a distal margin of >1 mm (Log-rank p = 0.09). Only stage ypT4 was an independent predictor of worse LRRFS (HR 15.14, p = 0.026). The 5-year LRRFS was significantly lower in TRG3-5 patients with a distal margin of ≤1 mm compared to those with a distal margin of >1 mm (68.5% vs. 84.2%, p = 0.027), while no difference was observed in case of TRG1-2 (p = 0.77). Low-responder rectal cancers after nCRT still require a distal margin of >1 mm to reduce the high likelihood of local relapse.