Differential effect of concurrent chemotherapy regimen on clinical outcomes of preoperative chemoradiotherapy for locally advanced rectal cancer

Purpose: The purpose of this study was to evaluate the differential effect of chemotherapy regimen in preoperative chemoradiotherapy (CRT) for locally advanced rectal cancer. Methods: The medical records of 279 patients who underwent preoperative CRT followed by surgery for cT3/4 rectal cancer from 2003 to 2010 were retrospectively reviewed. Thirty-four patients were treated with one cycle of i.v. bolus 5-fluorouracil (5-FU) during 1^st week (group A), 214 patients with two cycles of i.v. bolus 5-FU during 1^st and 5^th week (group B), and 31 patients with oral capecitabine on the days with radiotherapy (group C). Propensity score matching was performed between three groups. Results: Median follow-up was 60.1 months. Five-year locoregional recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), disease-free survival (DFS) and overall survival (OS) rates were 91.2, 83.3, 75.0, and 84.5%, respectively. Thirty-one patients per group were allocated to three groups via propensity score matching. On univariate analysis, concurrent chemotherapy regimen was not a significant prognostic factor for survival outcomes in the matched group analysis (OS, p=0.175; DFS, p=0.481; DMFS, p=0.515; LRFS, p=0.456). In addition, there was no significant difference in the sphincter preserving surgery rate, circumferential resection margin status, and pathologic response between three groups (p=0.441, 1.000, 0.818, respectively). As regards to treatment-related toxicity, 9 patients showed grade 3 neutropenia in group B, while there was no grade 3 or higher toxicity in groups A and C. Conclusion: The concurrent chemotherapy regimen (5-FU #1 vs 5-FU #2 vs capecitabine) did not have a significant effect on treatment outcomes in locally advanced rectal cancer patients receiving neoadjuvant CRT.