Cost-Effectiveness of Prophylactic Radiation in Patients with Asymptomatic Bone Metastases

Abstract

Radiation therapy represents a primary therapy for palliation of symptomatic bone metastases. Recently, a randomized trial found that radiation may prevent skeletal-related events (SREs) among patients with asymptomatic bone metastases. Skeletal-related events, such as pathologic fracture or spinal cord compression, cause considerable morbidity and decrements in quality of life. However, asymptomatic bone metastases are quite common and treating large numbers of these patients with radiation adds cost to the health care system. With this study we evaluated the cost-effectiveness of external beam radiation therapy for high-risk asymptomatic skeletal metastases. We built a microsimulation model for cancer patients with high-risk asymptomatic bone metastasis who received either prophylactic external beam radiation therapy or standard of care. The model incorporated costs, quality of life (measured by health utility), as well as the risk of skeletal-related events, and risk of death. We measured cost-effectiveness with the incremental cost-effectiveness ratio (ICER), with ICERs under $150,000 per quality-adjusted life-year (QALY) considered cost-effective. One way and probabilistic sensitivity analyses were used to test model uncertainty. Simulating the clinical course of 1,000,000 patients with asymptomatic bone metastases, we found that compared to standard of care, radiation therapy increased overall cost by $22,431 and improved effectiveness by 0.37 QALYs, resulting in an ICER of $60,400/QALY. The model was most sensitive to assumptions about survival and the monthly cost of cancer care. The base model assumed that prophylactic radiation reduced the risk of death by 50% (Hazard ratio [HR] 0.5). Prophylactic radiation remained cost-effective with HRs up to 0.98, though beyond an HR of 0.98 prophylactic radiation was no longer cost-effective. If the monthly cost of ongoing cancer care increased from our base estimate of $1917 to $5567, then prophylactic radiation was no longer cost effective. The model was not sensitive to assumptions about the cost of radiation, quality of life, or model time horizon. Probabilistic sensitivity analysis demonstrated that radiation therapy was cost-effective in >99% of iterations. This study found that prophylactic radiation may represent a cost-effective treatment option by reducing the risk of skeletal-related events among patients with asymptomatic bone metastases. Longer follow-up and additional research defining efficacy and optimal target populations who benefit most from prophylactic radiation will help confirm these findings.