Stereotactic Body Radiation Therapy for Nonspine Bone Metastases: A Case-Based Radiosurgery Society Review

Growing evidence supports stereotactic body radiation therapy (SBRT) over conventional radiation therapy for spine bone metastases, with an expanding role in nonspine bone metastases (NSBM). Our case-based review aims to inform radiation oncologists in the appropriate use of SBRT for representative cases of NSBM.

Three cases were selected for discussion: (1) rib, (2) skull base, and (3) femur. Relevant literature was reviewed, and areas for future investigation were discussed.

SBRT can be effectively delivered in NSBM with appropriate patient selection, target volume delineation, prescription dose, organs at risk (OARs) dose constraints, and treatment planning.

The Radiosurgery Society's case-based review offers guidance on the appropriate use of SBRT in NSBM with discussions and consensus recommendations from experts. SBRT can be considered for patients with oligometastatic disease with a favorable prognosis in whom the goal is durable local control and/or symptom relief. It can be considered for radioresistant histologies and improved OAR sparing. Available magnetic resonance imaging or positron emission tomography/computed tomography should be fused to improve target volume delineation. A clinical target volume margin, generally of 5 mm, should be considered to cover microscopic disease. As bones are easily visualized on daily images acquired for accurate and precise setup of patients, a planning target volume margin should be kept less than or equal to 3 mm. Although SBRT can be delivered in 1 fraction, fractionated SBRT may be preferred to meet dose constraints when the clinical target volume is adjacent to the OARs. NSBM of long bones that are weight bearing, lytic, or have a high MIRELS score should be evaluated by an orthopedic surgeon.