Tumor regression grade in locally advanced rectal cancer after neoadjuvant chemoradiotherapy: influencing factors and prognostic significance

Objective: The extent of tumor regression varies widely among patients who receive neoadjuvant chemoradiotherapy (NACRT) followed by total mesorectal excision (TME) surgery. We evaluated the tumor regression grade (TRG) classification of patients and analyzed factors related to TRG and its value in predicting prognosis in locally advanced rectal cancer (LARC). Methods: This study retrospectively analyzed the clinicopathologic data of 269 consecutive patients with LARC treated from February 2002 to October 2014. The grade of TRG was based on the extent of primary tumor replaced by fibrosis. Clinical characteristics and relative survival were retrospectively analyzed. Results: There were 269 patients, among whom 67 patients (24.9%) achieved TRG0, whereas 46 patients (17.1%) showed TRG3. TRG1 and TRG2 were both found in 78 patients (29.0%). Clinicopathologic factors that were related to TRG included post-NACRT carcinoembryonic antigen (CEA) level (P=0.002), clinical T stage (P=0.022), pathologic T stage (P<0.001) and pathologic lymph node status (P=0.003). The 5-year overall survival (OS) was 74.6%, 55.1%, 47.4%, 28.3% for TRG0, TRG1, TRG2, TRG3, respectively (P<0.001). The 5-year disease-free survival (DFS) was 64.2%, 47.4%, 37.2%, 23.9% for TRG0, TRG1, TRG2, TRG3, respectively (P<0.001). Based on multivariate analysis, TRG was a significant predictor for both OS (P=0.039) and DFS (P=0.043). Conclusion: Clinicopathologic factors such as post-NACRT CEA level, clinical T stage, pathological T stage and pathological lymph node status are significantly associated with TRG. TRG is an independent predictor of survival. Therefore, it is reasonable to include the TRG for clinicopathologic assessment.