Evaluation of Dworak grading system as a prognostic indicator after neoadjuvant chemoradiotherapy in rectal cancer patients.

e15053 Background: The objective of this study was to assess the prognostic role of Tumor Regression Grading (TRG) according to the Dworak system on progression free survival (PFS) after chemoradiotherapy (CRT) in locally advanced rectal cancer. Methods: In total, 159 patients with locally advanced rectal cancer who underwent neoadjuvant CRT from January 2007 and December 2016 were enrolled. PFS (any relapse after surgery) was tested against TRG (Dworak grade 1+2 versus Dworak grade 3+4) and other potential risk factors (age, gender, pre- and postoperative T-stage, pre- and postoperative N-stage, grading, lymph invasion, vessel invasion, chemotherapy regime, resection margin, treatment delay). Risk factors with a highly significant influence (p < 0.01) in the univariate Kaplan-Meier (KM) estimation were tested for independence using the multivariate cox regression model. Results: With a mean follow-up of 42.5 months, 5 years and 10 years estimated PFS for all patients was 60.1% and 49.1% respectively. Estimation of 5 years and 10 years PFS was 49.7% and 45.5% for TRG Dworak grade 1+2 (n = 109) and 83.8% and 67% respectively for TRG Dworak grade 3+4 (n = 50). This difference was highly significant (p < 0.001). Other highly significant risk factors were postoperative N-stage (negative versus positive), lymph invasion (L0 versus L1), and resection margin (R0 versus R1/2). In the multivariate analysis, only TRG and post-op N-stage were identified as independent risk factors for PFS. Conclusions: In this analysis, Dworak Tumor Regression Grading appears to be a prognostic marker for oncologic outcomes in locally advanced rectal carcinoma patients treated with neoadjuvant CRT.