The Short-term Effect of Neoadjuvant Chemoradiation on Anorectal Function in Low and Midrectal Cancer: Analysis Using Preoperative Manometric Data

Abstract

The purpose of this study was to evaluate the short-term preoperative effects of neoadjuvant chemoradiation on anorectal function, excluding the bias of postoperative impairment. We analyzed 80 patients on whom preoperative anorectal manometry data were available for both prechemoradiation and postchemoradiation. Patients were divided into 2 groups according to the tumor location; lower rectum (n = 52) and mid rectum (n = 28). The paired t test was used to compare prechemoradiation and postchemoradiation parameters including the mean resting pressure, maximum squeeze pressure, percentage asymmetry of the resting and squeeze sphincter, length of the high-pressure zone, rectal sensory threshold, and rectal compliance. In patients with a lower rectal cancer, there were significant differences in the percentage asymmetry of the squeeze sphincter (27.81 +/- 6.46 vs 25.38 +/- 5.93%, P < .01), length of the high-pressure zone (2.14 +/- 0.74 vs 2.33 +/- 0.72 cm, P = .05), and rectal compliance (1.14 +/- 0.41 vs 1.02 +/- 0.40 mL/mmHg, P = .04). In patients with midrectal cancer, only the mean resting pressure increased significantly (45.08 +/- 18.57 vs 52.83 +/- 17.87 mmHg, P < .01). Clinical symptom evaluation demonstrated a significant decrease in the number of defecations and the frequency of tenesmus. Neoadjuvant chemoradiation did not impair overall short-term sphincter function significantly, regardless of the location of the primary tumor. Although there was a decrease in rectal compliance, it seemed that the tumor-downsizing effect compensated the expected worsening of anorectal function in the early postchemoradiation period.