Late gastrointestinal and urogenital side-effects after radiotherapy--incidence and prevalence. Subgroup-analysis within the prospective Austrian-German phase II multicenter trial for localized prostate cancer.

PURPOSE: In general late side-effects after prostate cancer radiotherapy are presented by the use of actuarial incidence rates. The aim of this analysis was to describe additional relevant aspects of late side effects after prostate cancer radiotherapy.
MATERIALS AND METHODS: All 178 primary prostate-cancer patients were treated within the Austrian-German multicenter trial by three-dimensional radiotherapy up to a local dose of 70 Gy (low/intermediate-risk) or 74 Gy (high-risk), respectively. Late gastrointestinal/urogenital (GI/GU) side-effects were prospectively assessed by the use of EORTC/RTOG score. Maximum side-effects, actuarial incidence rate and prevalence rates, initial appearance and duration of ≥grade 2 toxicity were evaluated.
RESULTS: Median follow-up was 74 months. Late GI/GU side-effects ≥grade 2 were detected in 15% (27/178) and 22% (40/178). The corresponding 5-year actuarial incidence rates for GI/GU side-effects were 19% and 23%, whereas the prevalence was 1-2% and 2-7% after 5 years, respectively. Late side effects ≥grade 2 appeared within 5 years after radiotherapy in all patients with GI side-effects (27/27) and in 85% (34/40) of the patients with GU side-effects, respectively and lasted for less than 3 years in 90% (GI) and 98% (GU).
CONCLUSIONS: This study demonstrates that the majority of late GI and GU side effects after primary external beam radiotherapy for prostate cancer are transient. Using only actuarial incidence rates for reporting side effects may lead to misinterpretation or overestimation. The combination of incidence and prevalence rates provides a more comprehensive view on the complex issue of late side effects.