Predictive factors for tumour response after the neoadjuvant-treatment of rectal adenocarcinoma

Abstract

Abstract Purpose Standard of care for locally advanced rectal cancer is neoadjuvant chemoradiotherapy followed by surgery. This study identified predictive factors for tumour response in our series. Patients and methods Between January 2005 and December 2018, 292 patients with locally advanced rectal cancer treated by preoperative chemo-radiation before surgery were retrospectively analyzed. The radiation dose was 50.4 Gy with fluoropyrimidine-based chemotherapy regimens. Patients-tumour and treatment-factors were tested for influence on tumour down staging and regression grade using Mandard scoring system on surgical specimens (TRG). Results Median age was 69 years (range 39–87); 33.9% of patients was Stage II and 54.5% Stage IIIB. Tumour down staging occurred in 211 patients (73%), including 63 patients (21.6%) with ypT0 (documented T0 at surgery) and 148 patients (50.7%) with a satisfactory tumour regression grade defined as TRG2–3. Upper rectal tumours were identified to predictive factors for pathologic complete response by univariate analysis (p = 0.002). TRG1–3 was associated with intervals from chemo-radiation to surgery (p = 0.004); TRG1–3 rates were higher with longer intervals: 1.71% in ≤ 5 weeks, 23.63% in 6–8 weeks and 46.9% in ≥ 9 weeks; and PTV 50.4 ≥ 800cc (p = 0.06); 3 and 5 years survivals were 85% and 90% for the group as a whole. Among ypT0 cases, the overall survival was 91.1% without significantly different (p = 0.25) compared with the remaining group, 87.2%. Among ypT0 cases, the relapse-free survival was 94.5%, with significantly different (p = 0.03) compared with the remaining group 78.2%. There were no treatment-associated fatalities. Thirty-two patients (10.96%) experienced Grade III/IV toxicities (proctitis, ephitelitis and neutropenia). Conclusions Tumour localization was identified as predictive factors of pathologic complete response for locally advanced rectal cancer treated with preoperative chemo-radiation. Upper rectal tumours are more likely to develop complete responses. Delay in surgery was identified as a favorable predictive factor for TRG1–3. The relapse-free survival in pathologic complete response group was higher compared with non-pathologic complete response.