Frequency of Complicated Symptomatic Bone Metastasis Over a Breadth of Operational Definitions

Abstract Background Numerous randomized trials have demonstrated non-inferiority of single- versus multiple-fraction palliative radiotherapy (RT) in the management of “uncomplicated” bone metastases. Yet there is neither a clear definition of what constitutes a “complicated” lesion nor substantial data regarding the prevalence of such “complicating” features in clinical practice. Thus, we identify a range of evidence-based operational definitions of “complicated” symptomatic bone and characterize the frequency of such “complicating” features at a high-volume, tertiary care center. Methods and Materials A retrospective review of patients seen in consultation for symptomatic bone metastases between 3/1/2007-7/31/2013 at XXXX identified patient and disease characteristics. Descriptive statistics characterized the frequency of the following “complicating” features: prior RT, prior surgery, neuraxis compromise, pathologic fracture, and soft tissue component at the symptomatic site. A range of definitions for “complicated” bone metastases was evaluated based on combinations of these features. Uni- and multivariable logistic regression evaluated the odds of “complicated” bone metastases as a function of site of primary cancer and of the symptomatic target lesion. Results A total of 686 symptomatic bone metastases in 401 patients were evaluated. Percent of target sites complicated by prior RT was 4.4%, prior surgery was 8.9%, pathologic fracture was 20.6%, neuraxis compromise was 52.0% among spine and medial pelvis sites, and soft tissue component was 38.6%. Over 96 possible definitions of “complicated” bone metastases were identified. The presence of such “complicated” lesions ranged from 2.3% to 67.3%, depending on the operational definition used. Odds of a “complicated” lesion were significantly higher for spine sites and select non-breast histologies. Conclusions In this retrospective study, we found “complicated” symptomatic bone metastases may be present in up to two-thirds of patients. Literature review also demonstrates no clear standard definition of “complicated” bone metastases, potentially explaining underutilization of single-fraction palliative RT in this setting.