Impact of neoadjuvant chemoradiation on anal sphincter function in patients with carcinoma of the midrectum and low rectum.

HYPOTHESIS Preoperative chemoradiation for patients with stage II and III midrectal and low rectal cancer may improve survival and decrease local recurrence rate. We evaluated the long-term impact of neoadjuvant chemoradiation on anal sphincter function. DESIGN Prospective analysis. SETTING Tertiary referral center. PATIENTS From March 1, 1996, to January 31, 2002, 50 patients with midrectal and low rectal cancer who underwent total mesorectal excision were prospectively enrolled. INTERVENTIONS Patients received either surgical therapy alone (group 1, n = 22) or preoperative, combined chemoradiation (group 2, n = 28). Group 2 was divided into patients with midrectal (group 2A, n = 14) and low rectal (group 2B, n = 14) cancer. Anorectal manometry was performed preoperatively and a median of 384 days postoperatively. MAIN OUTCOME MEASURES Anal resting pressure, squeeze pressure, anal sphincter vector volumes, length of the high-pressure zone, sensory threshold of the pouch, and rectal capacity. RESULTS Preoperative manometric values were comparable between the groups. No statistically significant manometric differences occurred in group 1 postoperatively. Mean resting pressure (preoperative and postoperative, respectively: 89 +/- 35 mm Hg, 53 +/- 17 mm Hg), resting vector volume (605 +/- 324 cm( 3), 142 +/- 88 cm(3)), and maximal tolerable volume (144 +/- 29 mL, 82 +/- 44 mL) decreased significantly in chemoradiated patients postoperatively (P<.05). Manometric values of group 2B patients remained stable postoperatively, while mean resting pressure (73 +/- 22 mm Hg vs 52 +/- 14 mm Hg) and resting vector volume (631 +/- 288 cm(3) vs 145 +/- 78 cm(3)) decreased significantly in group 2A patients (P<.001). CONCLUSIONS Total mesorectal excision does not influence anal sphincter function during long-term follow-up. Neoadjuvant chemoradiation results in disordered anal sphincter function in patients with midrectal cancer. Low and rectoanal anastomosis seems to obtain better anal sphincter function than higher anastomosis in chemoradiated patients.