Tumor regression grades: Potential outcome predictor of locally advanced rectal adenocarcinoma after preoperative radiotherapy

AIM: To analyze tumor regression grade (TRG) for prognosis of locally advanced rectal adenocarcinoma (LARA) treated with preoperative radiotherapy. METHODS: One hundred and ninety patients with clinical stage II/III LARA were studied. All patients underwent radical surgery (between 2004 and 2010) after 30-Gy/10-fraction preoperative radiotherapy (pre-RT). All 190 patients received a short course of pre-RT and were reassessed for disease recurrence and survival; the slides of surgical specimens were reviewed and classified according to Mandard TRG. We compared patients with good response (Mandard TRG1 or TRG2) vs patients with bad/poor response (Mandard TRG3-5). Outcomes evaluated were 5-year overall survival (OS), 5-year disease-free survival (DFS), and local, distant and mixed recurrence. Fisher's exact test or chi(2) test, log-rank test and proportional hazards regression analysis were used to calculate the probability that Mandard TRG was associated with patient outcomes. RESULTS: One hundred and sixty-six of 190 patients (87.4%) were identified as Mandard bad responders (TRG3-5). High Mandard grade was correlated with tumor height (41.7% < 6 cm vs 58.3% >= 6 cm, P = 0.050), ypT stage (75% ypT0-2 vs 25% ypT3-4, P = 0.000), and ypN stage (75% ypN0 vs 25% ypN1, P = 0.031). In univariate survival analysis, Mandard grade bad responders had significantly worse OS and DFS than good responders (TRG1/2) (OS, 83.1% vs 96.4%, P = 0.000; DFS, 72.3% vs 92.0%, P = 0.002). In multivariate survival analysis, Mandard bad responders had significantly worse DFS than Mandard good responders (DFS 3.8 years (95% CI: 1.2-12.2 years, P = 0.026). CONCLUSION: Mandard grade good responders had a favorable prognosis. TRG may be a potential predictor for DFS in LARA after pre-RT.