Abstract
PURPOSE: Older patients undergoing radiation therapy (RT) for pelvic malignancies are at increased risk for pelvic fracture, which is associated with significant morbidity and mortality. RT techniques such as brachytherapy or intensity modulated RT (IMRT) allow for more conformal dose distributions, but it is not known whether the risk for pelvic fracture varies by RT modality. METHODS AND MATERIALS: This observational cohort study involved 28,354 patients ≥65 years old, treated with RT for pelvic malignancies. We evaluated the relative risk of pelvic fracture by type of RT when accounting for baseline factors. To test for nonspecific effects, we also evaluated risk of nonpelvic fractures in the same population. RESULTS: The 5-year incidence of pelvic fractures was 12.7% (95% confidence interval [CI], 11.6%-13.8%), 11.8% (10.8%-12.8%), and 3.7% (3.4%-4.0%) for patients with gastrointestinal, gynecologic, and prostate cancer, respectively. On multivariable analysis, being treated with IMRT (hazard ratio, 0.85; 95% CI, 0.73-0.99) or brachytherapy therapy alone (hazard ratio, 0.43; 95% CI, 0.34-0.54) was associated with a reduced hazard for pelvic fractures compared with 3D conformal radiation therapy in female patients. In contrast, there was no association with RT modality and the hazard for nonpelvic fractures among females. There was no significant association between pelvic fractures and IMRT or brachytherapy for male patients. White race, advanced age, and higher comorbidity were associated with an increased hazard for pelvic fracture. CONCLUSIONS: IMRT and brachytherapy were associated with a reduced risk of pelvic fractures in older women undergoing RT for pelvic malignancies. Pelvic insufficiency fracture risk should be considered when treating with pelvic RT.