The pattern of bowel dysfunction in patients with rectal cancer following the multimodal treatment: anorectal manometric measurements at before and after chemoradiation therapy, and postoperative 1 year

PURPOSE: Bowel dysfunction commonly occurs in patients with locally advanced rectal cancer treated with a multimodal approach of chemoradiation therapy (CRT) combined with sphincter-preserving rectal resection. This study investigated the decline in anorectal function using sequential anorectal manometric measurements obtained before and after the multimodal treatment as well as at a 1-year follow-up. METHODS: This was a retrospective cohort study conducted in a single center. The study population consisted of patients with locally advanced mid- to low rectal cancer who received the preoperative CRT followed by sphincter-preserving surgery from 2012 to 2016. The anorectal manometric value measured after each treatment modality was compared to demonstrate the degree of decline in anorectal function. A generalized linear model of repeated measures was performed using the manometric values measured pre- and post-CRT, and at 12 months postoperatively. RESULTS: Overall, 100 patients with 3 consecutive manometric data were included in the final analysis. In the overall cohort study, the mean resting and maximal squeezing pressures showed insignificant decrement post-neoadjuvant CRT. At a 1-year postoperative follow-up, the maximal squeezing pressure significantly decreased. The maximal rectal sensory threshold demonstrated significant reduction consecutively after each following treatment (P<0.001). CONCLUSION: The short-term effect of neoadjuvant CRT on the anal sphincters was relatively trivial. The following sphincter-saving surgery resulted in a profound disruption of the anorectal function. Patients with rectal cancer should be consulted on the consequence of multimodal treatment.