Radiation Therapy for Asymptomatic Bone Metastases

Skeletal-related events (SREs) in patients with cancer metastases to bone can be reduced by 10% to 20% with bone-modifying agents (e.g., bisphosphonates). Although radiation therapy is used to palliate painful bone metastases, data regarding its use in the asymptomatic setting are limited.

In this multicenter, phase 2 clinical trial, investigators compared prophylactic radiation therapy against standard of care for high-risk, asymptomatic bone metastases. Seventy-eight adults with widely metastatic solid tumor malignancies and 122 bone metastases were randomized to receive radiation therapy or standard of care (systemic therapy or observation). The most common primary cancers were lung (27%), breast (24%), and prostate (22%). The trial's primary outcome was SREs, defined as pathologic fracture, spinal cord compression, orthopedic surgery, or palliative radiation therapy for pain.

The radiation therapy arm had a significant reduction in SREs compared with the standard care arm (1.6% vs. 28.6%; P<.001). Additionally, significantly fewer patients in the radiation arm were hospitalized for SREs (0 vs. 11%, respectively; P=.045). Overall survival was longer in the radiation arm than the standard care arm (median, 1.7 vs. 1.0 years; hazard ratio, 0.49; P=0.18), but the study was not powered for this outcome. Among patients who were not on an opioid at study entry, opioid-free probability did not differ between arms (HR, 0.57; P=0.5). Treatment-related complications were uncommon, and no grade 3 or higher radiation-related adverse events were reported.