Comparing long-term toxicity between external beam radiotherapy modalities: A SEER/Medicare database study.

118 Background: The use of intensity modulated radiotherapy (IMRT) for the treatment of prostate cancer (CaP) has been widely promoted due to the hypothesized benefit of low late toxicity. Methods: The SEER-Medicare database was queried for CaP patients treated with external beam radiotherapy (EBRT), 1991-2007. CPT billing codes were used to identify patients treated with IMRT or standard EBRT (sEBRT), which was comprised of conformal radiotherapy or a four-field technique. Patients without a treatment billing code were excluded from the analysis. Information on dose is unavailable. CPT codes were also used to identify procedures associated with gastrointestinal (GI) or genitourinary (GU) toxicity related treatments. Cumulative incidence rates for GI and GU toxicity were calculated with death treated as a competing event. Results: A total of 137,427 patients who were 65 years or older at the time of CaP diagnosis and who had CaP as their only cancer diagnosis were retrieved from the SEER-Medicare database...