Abstract
BACKGROUND: Late anorectal toxicity is a frequent adverse event of external beam radiotherapy (EBRT) for prostate cancer. The pathophysiology of anorectal toxicity remains unknown, but we speculate that rectal distensibility is impaired due to fibrosis. Our goal was to determine whether EBRT induces changes of rectal distensibility as measured by an electronic barostat and to explore whether anorectal complaints are related to specific changes of anorectal function. METHODS: Thirty-two men, irradiated for localized prostate carcinoma, underwent barostat measurements, anorectal manometry, and completed a questionnaire prior to and 1 year after radiotherapy. The primary outcome measure was rectal distensibility in response to stepwise isobaric distensions. In addition, we assessed sensory thresholds, anal pressures, and anorectal complaints. KEY RESULTS: External beam radiotherapy reduced maximal rectal capacity (227 +/- 14 mL vs 277 +/- 15 mL; P < 0.001), area under the pressure-volume curve (3212 +/- 352 mL mmHg vs 3969 +/- 413 mL mmHg; P < 0.005), and rectal compliance (15.7 +/- 1.2 mL mmHg(-1) vs 17.6 +/- 0.9 mL mmHg(-1) ; P = 0.12). Sensory pressure thresholds did not significantly change. Sixteen of the 32 patients (50%) had one or more anorectal complaints. Patients with urgency (n = 10) had a more reduced anal squeeze and maximum pressure (decrease 29 +/- 11 mmHg vs 1 +/- 7 mmHg; P < 0.05 and 31 +/- 12 mmHg vs 2 +/- 8 mmHg; P < 0.05 respectively) compared with patients without complaints, indicating a deteriorated external anal sphincter function. CONCLUSIONS & INFERENCES: Irradiation for prostate cancer leads to reduced rectal distensibility. In patients with urgency symptoms, anal sphincter function was also impaired.
