Endorectal balloon reduces anorectal doses in post-prostatectomy intensity-modulated radiotherapy

Abstract: Background and purpose: To investigate the effect of an endorectal balloon (ERB) on anal wall (Awall) and rectal wall (Rwall) doses in high-dose post-prostatectomy intensity-modulated radiotherapy (IMRT). Materials and methods: For 20 patients, referred for salvage IMRT after prostatectomy for prostate cancer, two planning CT-scans were performed: one with and one without an air-filled ERB. A planning target volume (PTV) was defined, using international guidelines. Furthermore, the Awall and Rwall were delineated. In both the scans, IMRT plans were generated with a prescribed dose of 70Gy. The mean dose (D mean), maximum dose, minimum dose, and volumes exposed to doses ranging from ⩾20 to ⩾70Gy (V 20–V 70) to the Awall and Rwall were calculated. Finally, inner Rwall surface areas exposed to doses ranging from ⩾20 to ⩾70Gy (A 20–A 70) were calculated. Dose-parameters were compared between plans with and without ERB. Results: All Awall parameters, except V 70, were significantly reduced by the ERB with an overall D mean reduction of 6Gy. Absolute reductions in dose–volume parameters varied from 5% to 11%. Significantly reduced Rwall V 30, V 40, and A 40 were observed with ERB, irrespective of the target volume size. Conclusion: ERB application significantly reduces Awall and to a lesser degree Rwall doses in high-dose post-prostatectomy IMRT. [Copyright &y& Elsevier]