Neorectal hyposensitivity after neoadjuvant therapy for rectal cancer.

Abstract

Preoperative radiotherapy for rectal cancer has a detrimental effect on long-term anorectal function and quality of life, additional to that observed after rectal resection. The exact physiological mechanisms for the excess impairment remain unknown. We aimed to investigate neorectal and anal sphincter properties in patients treated with neoadjuvant therapy (NT) prior to total mesorectal excision (TME). Sixteen patients (NT+ patients) were examined by multimodal neorectal stimulation and standard anorectal physiological testing. Data were compared to the results of 23 patients, who underwent TME without NT (NT- patients). NT+ patients had elevated sensory thresholds to heat (median temperature, 60 vs. 55 °C; p<0.01) and mechanical distension (median tension, 2513 vs. 1521 mmHg mm; p=0.05) in the fasting state, and altered perception of the sensory response to heat (p=0.01) and cold (p=0.01) compared to NT- patients. No differences in the biomechanical properties of the neorectal wall were detected. Anal resting pressure was lower in NT+ patients compared to NT- patients (median pressure, 31 vs. 45 cm H2O; p=0.05). Pelvic radiotherapy causes neorectal hyposensitivity to mechanical and thermal stimuli in patients receiving NT prior to TME surgery for rectal cancer, possibly due to impaired afferent nerve function.