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.