Background
Stereotactic body radiation therapy (SBRT) is an increasingly utilized therapy for primary and metastatic lung tumors. Despite promising tumor control, SBRT is associated with increased risk of rib osteoradionecrosis leading to rib fracture. We aimed to 1) determine clinical, demographic, and procedural risk factors of osteonecrosis and 2) radiographically characterize rib osteonecrotic fractures.
Methods
We retrospectively identified 106 patients who underwent SBRT between 2015 and 2018 for a primary or metastatic lung neoplasm with a minimum of 12 months of follow up. Patients with incomplete records, prior ipsilateral thoracic radiotherapy, or relevant trauma were excluded. Computed tomography (CT) scans were reviewed to identify and characterize rib fractures. Multivariate logistic regression modeling was used to elucidate clinical, demographic, and procedural risk factors (e.g., age, sex, race, medical comorbidities, dosage, and tumor location).
Results
A total of 106 patients with 111 treated tumors satisfied the inclusion criteria, 35 (32%) of whom developed at least one fractured rib (60 total ribs). The maximum number of affected ribs per subject was five. Multivariate regression identified posterolateral location as an independent risk factor for rib fracture. Radiographically, fractures in 77% of affected subjects showed discontinuity between healing edges.
Discussion
Post-SBRT fractures demonstrated distinct discontinuity, a possible signal of osteoradionecrosis. Tumor location along the posterolateral chest wall was the only independent predictor of rib fracture. Given its increasing frequency of use, understanding the risk profile of SBRT is vital to maintain patient safety and appropriately inform patient expectations
