Functional Outcomes and Toxicities Associated with SBRT to Bone Metastases Involving the Joint Space

Abstract

Metastatic spread to bone is a common occurrence in advanced malignancies. Stereotactic Body Radiation Therapy (SBRT) is increasingly used for management of bone metastases in both the palliative and oligometastatic settings, especially for radioresistant histologies. Historically, therapeutic radiation to joints has been avoided whenever possible to minimize toxicities such as joint fibrosis and stiffness. Very little data exists to guide the treatment of bone metastases involving or adjacent to the joint space using SBRT. The purpose of this study is to report functional outcomes and toxicities associated with SBRT to metastatic bone lesions involving the joint space. Patients with solid tumor bone metastases involving the joints of long bones who were treated with SBRT (≥500 cGy/fraction; BED10 ≥37.5) who had ≥30 days follow up were identified from our institutional electronic health record using an IRB approved protocol. Pre-treatment and post-treatment pain assessments and toxicities were collected and scored retrospectively. Toxicities were categorized as acute (≤30 days post treatment) or late (>30 days post-treatment). Weidentified 40 evaluable patients with 54 lesions treated with SBRT. Lesions treated included those involving the hip (29/54, 54%), shoulder (11/54, 20%), elbow (8/54, 14%), and knee (6/54, 11%). The most common patient histology treated was renal cell carcinoma (13/40, 33%), followed by prostate adenocarcinoma (7/40, 18%), non-small cell lung cancer (4/40, 10%), and breast cancer (4/40, 10%). The remainder (12/40) had other histologies. Median follow up time was 7.7 months (range = 1.3-55.0). Median prescribed dose was 650 cGy/fraction (range = 500-1300 cGy) and most lesions received 4000 cGy in 5 fractions (18/54, 33%). At >30 days, of the 42 sites where pain was reported pre-treatment, 30/42 (71%) had complete or partial pain relief, while 10/42 (24%) experienced no pain relief during available follow up. Patients reported worsening pain after SBRT in 2/54 (3.7%) of treated lesions. Seven of 54 (14.0%) treated lesions led to complaints of joint stiffness requiring physical therapy. A minority of patients developed insufficiency fractures or treatment failures after SBRT requiring surgery (4/54, 7.4%). Three of 54 patients (5.6%) developed symptomatic radiation myositis confirmed on imaging. Toour knowledge, this is the first study to report functional and toxicity outcomes of SBRT to lesions involving the joints of long bones. While SBRT appears to have acceptable toxicities at the doses reported in this analysis, further study is warranted to identify pre-treatment factors predictive of toxicity. Limitations of the study include its small sample size, retrospective nature, and single institution design. Future studies will focus on dosimetric and clinical factors associated with toxicities which may allow for more personalized treatments and assist with informed consent.