Feasibility Of Relatively Low Neoadjuvantradiation Doses For Locally Advanced Rectal Cancer: A Propensity Score-Matched Analysis

BackgroundNeoadjuvant chemoradiation therapy is part of the standard treatment of locally advanced rectal cancer (LARC). Although various options for modifying preoperative radiotherapy protocols have been researched and proposed, there is still no consensus as to the most appropriate dose regimen of neoadjuvant therapy for this disease.AimTo evaluate the effects of relatively low-dose radiation regimens on tumor regression and clinical outcomes in rectal cancer patients treated with neoadjuvant CRT followed by mesorectal excision.Methods and ResultsWe retrospectively analyzed patients with LARC who underwent neoadjuvant concurrent chemoradiation (CCRT) in our hospital from June 2010 to December 2015. A total of 259 consecutive patients were enrolled, receiving 42 to 44 Gy (RLD, n = 31), 46 Gy (SD1, n = 69), or 50 Gy (SD2, n = 159) of CRT, combined with either capecitabine/oxaliplatin or capecitabine only or mFOLFOX6, followed by total mesorectal excision. A 1:4 propensity score matching was employed, and all patients in the RLD group were matched with 124 patients in the SD2 group. Rates of pCR, 3-year local/regional recurrence (LRR), overall survival (OS), and disease-free survival (DFS) in the RLD group were all not significantly different (0.313 for pCR; 0.884 for LRR; and 0.762 for OS; 0.101 for DFS) from those in SD1 and SD2 groups. The RLD group showed a lower incidence of grade 3 to 4 hematologic toxicity than SD2 group (0.019). A propensity score analysis demonstrated no significant differences in the pCR rates and 3-year outcomes between the RLD and SD2 group.ConclusionRelatively low-dose regimen (<= 44 Gy) of neoadjuvant CRT combined with standard concurrent chemotherapy appears to be both safe and effective in Chinese patients with LARC. Further testing by prospective randomized trials is needed.