What is the role of Stereotactic Body Radiation Therapy (SBRT) for bone metastases?

From the Guidelines

Stereotactic body radiation therapy (SBRT) is a highly effective treatment option for bone metastases, providing excellent pain relief and local tumor control, and should be considered as a first-line treatment for patients with oligometastatic disease or those who have failed conventional radiation therapy. SBRT delivers high doses of precisely targeted radiation in fewer treatments (typically 1-5 sessions) compared to conventional radiation therapy. For bone metastases, common SBRT dose regimens include 16-24 Gy in a single fraction, 24-27 Gy in 3 fractions, or 30-40 Gy in 5 fractions, with the specific dose depending on the location, size, and proximity to critical structures 1.

Key Benefits of SBRT

• Excellent pain relief: 70-90% of patients experience significant pain reduction 1
• Local tumor control: 80-90% at one year 1
• Minimal side effects: rare complications such as vertebral compression fractures (occurring in approximately 10-20% of spinal treatments) 1
• Temporary pain flare may occur 1-3 days after treatment in about 20% of cases, which can be managed with short-term corticosteroids (dexamethasone 4-8 mg daily for 3-5 days) and analgesics 1

Patient Selection

• Oligometastatic disease (1-5 metastases)
• Failed conventional radiation therapy
• Performance status and expected clinical benefits should be considered when selecting patients for SBRT 1

Treatment Considerations

• Location, size, and proximity to critical structures should be considered when determining the specific SBRT dose regimen 1
• Patients should be monitored for rare complications such as vertebral compression fractures 1
• SBRT can be used in combination with other treatments, such as surgery and systemic therapies, to optimize local control and prevent skeletal-related events (SREs) 1

From the Research

Stereotactic Body Radiotherapy (SBRT) for Bone Metastases

• SBRT is a promising treatment for bone metastases, offering considerable pain relief, durable tumor control, and efficacy against radioresistant tumors 2.
• The treatment enables the delivery of high doses of radiation to bone lesions by maximizing dose conformality, yielding several clinical advantages 2.
• SBRT has the potential to overcome the limitations of conventional external beam radiotherapy (cEBRT), including short duration of pain relief, limited long-term tumor control, and suboptimal efficacy against radioresistant tumors 2.

Clinical Scenarios and Evidence

• Painful spinal metastases, painful non-spinal bone metastases, and metastatic epidural spinal cord compression are three clinical scenarios where SBRT has shown utility and potential as an emerging treatment option 2.
• Single-fraction SBRT has advantages, including shorter overall duration of treatment, absence of inter-fraction uncertainty, improved compliance, theoretical increased efficacy, and lower costs 3.
• However, caution is advised due to reports of severe late toxicities, such as vertebral collapse fracture (VCF) 3.

Efficacy and Toxicity of SBRT

• A prospective study assessing the efficacy and toxicity of SBRT for oligometastatic bone metastases found that SBRT is effective and tolerable in patients with oligometastatic bone disease 4.
• The study reported a 2-year local progression-free survival of 84.8%, 2-year progression-free survival of 47.5%, and 2-year overall survival of 87.3% 4.
• Treatment-related toxicities were reported in 26.5% of patients, with no severe late toxicities observed 4.

Prognostic Factors and Outcomes

• A study evaluating the safety of SBRT of bone metastases in oligometastatic disease found that positron emission tomography response was a strong prognostic factor of local control 5.
• The study also found that oligometastatic status and small planning target volume (PTV) size could identify a subset of oligometastatic patients at better prognosis 5.
• A literature review of SBRT in non-spine bone metastases found that SBRT can result in better local control and pain management in non-spine bone metastases patients, with a low rate of side effects 6.