The effect of postoperative beam, implant, and combination radiation therapy on GI and bladder toxicities in female Medicare beneficiaries with stage I uterine cancer.

OBJECTIVE: Determine the risk of late gastrointestinal (GI) and bladder toxicities in women treated for Stage I uterine cancer with postoperative beam, implant, or combination radiation. METHODS: The Surveillance, Epidemiology, and End Results (SEER) tumor registry and Medicare claims were used to estimate the risk of developing late GI and bladder toxicities by type of radiation received. Bladder and GI diagnoses were identified 6-60 months after cancer diagnosis. Cox-proportional hazard models were used to estimate risk of any late GI or bladder toxicity due to type of radiation received. RESULTS: A total of 3,024 women with uterine cancer diagnosed from 1992-2005 were identified for analysis with a mean age of 73.9 (Standard Deviation (SD) ± 6.5). Bladder and GI toxicities occurred most frequently in the combination group, and least in the implant group. After controlling for demographic characteristics, tumor grade, diagnosis year, SEER region, comorbidities, prior GI and bladder diagnosis, and chemotherapy, women receiving implant radiation had a 21% absolute decrease in GI toxicities compared to women receiving combination radiation (Hazard Ratio (HR) 0.79, 95% confidence interval (CI) 0.68-0.92). No differences were observed between those receiving beam and combination in GI (HR 1.01 (0.89-1.14)) and bladder (HR 0.95 (0.80-1.11)) toxicities. CONCLUSIONS: Older women receiving combined radiation had the highest rates of GI and bladder toxicities, while women receiving implant radiation alone had the lowest rates. When selecting type of radiation for a patient, these toxicities should be considered. Counseling older women surviving cancer on late toxicities due to radiation must be a priority for physicians caring for them.