Purpose: Late side effects were prospectively evaluated up to 5 years after dose-escalated external beam radiotherapy (EBRT) and were compared with a previously treated series with conventional conformal technique.
Methods and materials: Bladder and bowel symptoms were prospectively evaluated with the Prostate Cancer Symptom Scale (PCSS) questionnaire up to 5 years posttreatment. In all, 257 patients completed the questionnaire 5 years posttreatment. A total of 168 patients were treated with the conformal technique at doses<71 Gy, and 195 were treated with the dose-escalated stereotactic BeamCath technique comprising three dose levels: 74 Gy (n=68), 76 Gy (n=74), and 78 Gy (n=53).
Results: For all dose groups analyzed together, 5 years after treatment, urinary starting problems decreased and urinary incontinence increased in comparison to baseline values. No increase in other bladder symptoms or frequency was detected. When comparing dose groups after 5 years, both the 74-Gy and 78-Gy groups reported increased urinary starting problems compared with patients given the conventional dose (<71 Gy). No increased incontinence was seen in the 76-Gy or the 78-Gy groups. Bowel symptoms were slightly increased during the follow-up period in comparison to baseline. Dose escalation with stereotactic EBRT (74-78 Gy) did not increase gastrointestinal late side effects after 5 years in comparison to doses<71 Gy.
Conclusion: Dose-escalated EBRT with the BeamCath technique with doses up to 78 Gy is tolerable, and the toxicity profile is similar to that observed with conventional doses<71 Gy.