Gastrointestinal toxicity of transperineal interstitial prostate brachytherapy.

Abstract

To characterize the severity and time course of rectal toxicity following transperineal prostate brachytherapy using prospectively recorded data, and to determine factors associated with toxicity. One hundred thirty-four patients with prostate cancer treated with transperineal brachytherapy from 1997 to 1999 had rectal toxicity data available for analysis. Patients with Gleason score (GS) > 6, prostate-specific antigen (PSA) > 6, or stage > T2a were treated initially with external beam radiation therapy followed by brachytherapy boost; patients with none of these features were treated with brachytherapy alone. Both iodine-125 and palladium-103 sources were used, and loaded according to a modified Quimby distribution. At each follow-up, toxicity was recorded according to a modified RTOG gastrointestinal scale. Thirty-nine percent of patients experienced gastrointestinal toxicity, mostly Grade 1. Median duration of symptoms was 6 months. Two patients experienced Grade 3 toxicity, both of whom had minimal symptoms until their 12-month follow-up. There was no Grade 4 or 5 toxicity. The addition of external beam radiation therapy (p = 0.003), higher clinical stage (p = 0.006), and Caucasian race (p = 0.01) were associated with increased incidence of toxicity. Most patients with rectal toxicity have very mild symptoms. There is a small risk of severe late toxicity. External beam radiation, higher stage, and race are associated with toxicity.