SUN JUNG KIM

Background This study aimed to review the magnetic resonance imaging (MRI) features of patients with low rectal cancer (LRC) undergoing preoperative chemoradiotherapy (CRT) and investigate the risk factors for treatment failure after sphincter preserving surgery following preoperative CRT based on multidisciplinary approach. Objectives Patients who underwent standard CRT and sphincter preserving radical surgery for LRC between January 2000 and December 2011 were retrospectively reviewed. Sphincter preservation failure (SPF) was defined as any one of the following: positive pathologic circumferential resection margin, local recurrence, failure to repair ileostomy, or permanent stoma formation due to anastomotic complications. Results Among the 191 patients, there were no overall significant differences between sphincter preservation success ( n = 161) and SPF (n = 30) groups. SPF group showed a higher MRI circumferential resection margins (mrCRM) positive rate before and after CRT (before CRT: 33.3% vs. 16.1%, p = 0.027; after CRT: 23.3% vs. 6.2%, p = 0.002). Multivariate analysis showed that only mrCRM after CRT was associated with SPF (hazard ratio = 4.596, p = 0.005). SPF group showed worse 5‐year cancer‐specific survival (51% vs. 92.7%, p < 0.001). Conclusions MRI‐based assessment of the tumor after CRT plays a crucial role in predicting the success and feasibility of sphincter preservation as well as oncological outcomes in patients with LRC.