Determining whether postoperative chemoradiotherapy is required in patients with pathologic T3N0 rectal cancer with negative resection margin

Purpose This study aimed to identify the risk factors for locoregional recurrence (LR) and determine possible candidates for postoperative concurrent chemoradiotherapy (CCRT) in pathologic T3N0 (pT3N0) rectal cancer patients with a negative resection margin after total mesorectal excision (TME). Method Data from 365 patients who had pT3N0 rectal cancer between 2003 and 2012 in the Samsung Medical Center were reviewed. All patients underwent upfront surgery without preoperative treatment. Postoperative management involved either no adjuvant therapy (n =122), chemotherapy alone (n =100), or CCRT (n =143). Results The median follow-up duration was 71 months. The 5-year overall survival, disease-free survival, and LR-free survival (LRFS) rates were 95.9%, 86.9%, and 96.3%, respectively. When comparing the three groups (surgery alone [n =122], chemotherapy alone [n =100], and CCRT [n =143]), there was no significant difference in LRFS among them (94.0%, 93.4%, and 99.2%, respectively;p =0.20). However, when patients were stratified by risk factors (distance from anal verge <= 5 cm and distal resection margin [DRM] <= 2 cm), the 5-year LRFS improved by more than 10% by adding CCRT (98.9% with CCRT vs. 87.4% without CCRT,p= 0.006) in those with more than one risk factor. Postoperative CCRT did not affect the 5-year LRFS (100% with CCRT vs. 99.0% without CCRT,p= 0.66) in patients with no risk factors. Conclusion Postoperative CCRT significantly decreased LR in patients with pT3N0 rectal cancer with a negative resection margin but having a distance from the anal verge <= 5 cm or DRM <= 2 cm.