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Purpose: To report patient tolerance and acute anorectal toxicity of an endorectal balloon used for prostate immobilization during 35 daily fractions.

Materials and Methods: The records of 396 patients treated for prostate cancer from October 1997 to November 2001 were reviewed. Patients were treated with intensity modulated radiation therapy (IMRT). Endorectal balloon catheter was inserted daily, inflated with 100 mL of air for immobilizing the prostate gland. Patient and treatment factors were analyzed. Patients received a mean dose of 77 Gy/35 fractions/7 weeks with no rectal block.

Results: None of the 396 patients halted treatment because of associated ano-rectal toxicity. No patient stated that he would decline to be treated again with rectal balloon. Three of 396 (0.8%) patients required a reduction in the volume of the balloon to 50 mL. Seventeen of 396 (4.3%) patients required Lidocaine jelly with the insertion of balloon. Radiation Therapy Oncology Group (RTOG) grades 1 and 2 rectal toxicity occurred in 55/396 (13.9%) and 73/396 (18.4%), respectively. No RTOG grade 3 or 4 toxicities occurred. Topical anal medications were prescribed for 46 of 396 (11.6%) patients and antidiarrhea medication for 27 of 396 (6.8%) patients. Of patients with pretreatment anorectal disease, 50% developed rectal toxicities over the 7 weeks. Rectal toxicity occurred most frequently in the third, fourth, fifth, or sixth week; 19.5%, 20.8%, 18.2%, and 16.9%, respectively. The duration of the toxicity measured lasted 1 week, 35.2%; 2 weeks, 31.0%; 3 weeks, 15.5%; 4 weeks, 11.3%; 5 weeks, 4.2%; and 6 weeks, 2.8%.

Conclusion: Most of the patients, 393/396 (99.2%), tolerated a 100 mL endorectal immobilization balloon for IMRT. The rate of acute anorectal toxicity was acceptable with no grade 3 or 4 toxicities. Duration of the toxicities typically was 1 to 2 weeks. Patients with pre-existing anorectal disease are at higher risk of developing acute anorectal toxicity with the use of an endorectal balloon.

(C) 2006 Lippincott Williams & Wilkins, Inc.