Prophylactic Radiation Therapy for High-Risk Asymptomatic Bone Metastases

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1. The hazard ratio of skeletal-related events in patients treated with radiation compared with patients who were not treated with radiation was 0.09.

2. There were no grade 3 or higher treatment-related adverse events.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Many patients with bone metastases experience skeletal-related events (SRE). While radiation therapy is known to help with painful bone metastases, its role in asymptomatic cases is not well-established. Prior research suggested a link between radiation and a lower risk of SRE. This randomized study investigates if radiation for asymptomatic high-risk bone metastases could reduce SRE. The primary outcome measure was number of SRE (pathologic fractures, spinal cord compression, orthopedic surgery to bone, and/or palliative RT for pain), and the secondary outcome measures includes hospitalizations for SRE, overall survival (OS), opioid-free survival, patient reported outcomes, and adverse events. It was overall found that patients in the RT arm compared to SoC arm had hazard ratio 0.09 for SRE. The rate of hospitalization for SRE was 0% in the RT arm vs 11% in the SoC arm. The median OS was 1.7 years in the RT arm vs 1.0 years in the SoC arm, with HR 0.46. There was no significant difference found between both arms with regards to opioid-free probability. Average pain (measured by BPI) across both arms was not significant in 3 or 6 months, but was significant at 12 months, with an average score decrease of -2.0. Quality of life was not significantly different between study arms. There were no grade 3 or higher treatment-related adverse events. The strengths of this study included its methodology (RCT) and the limitations included its small sample size. Overall, it was found that radiation therapy had favorable outcome measures compared to standard of care in patients with asymptomatic high risk bone metastases.

Click to read the study in JCO

Click to read an accompanying editorial in JCO

Relevant Reading: External beam radiation therapy (EBRT) for asymptomatic bone metastases in patients with solid tumors reduces the risk of skeletal-related events (SREs)

In-Depth [randomized controlled trial]: This multicenter, phase II clinical trial randomized adults with histologically confirmed solid tumor cancer with at least 1 asymptomatic high-risk bone metastasis (≥2 cm, or disease involving the hip, shoulder, sacroiliac joints, long bones, or vertebrae of the junctional spine) into standard of care with either systemic therapy or observation (SoC, 39 patients, 49 bone metastases) or radiation therapy (RT, 39 patients, 62 bone metastases). Dosing of RT was determined by the treating radiation oncologist but the most common treatment regimens for the RT group were 27 Gy in three fractions, 20 Gy in five fractions, and 8 Gy in one fraction. Most common primary cancer types were lung (27%), breast (24%), and prostate (22%). With a 1-year follow-up period, 1.6% of bone metastases in the RT arm were observed to have SRE vs 29% in the SoC arm, p < .001. It was overall found that patients in the RT arm compared to SoC arm had hazard ratio 0.09 (95%CI, 0.01-0.66, p=.018). The rate of hospitalization for SRE was 0% in the RT arm vs 11% in the SoC arm, p=0.045. The median OS (with median follow-up of 2.5 years) was 1.7 years (95%CI, 1.3-NR) in the RT arm vs 1.0 years (95%CI, 0.8-1.9) in the SoC arm, with HR 0.46 (95%CI, 0.25-0.83, p=.01). There was no significant difference found between both arm with regards to opioid-free probability (HR 0.57, 95%CI, 0.1-3.4, p=.5). Average pain (measured by BPI) across both arms was not significant in 3 or 6 months, but was significant at 12 months, -2.0 (95%CI, -3.9 to -0.1, p=.039). Quality of life was not significantly different between study arms. There were no grade 3 or higher treatment-related adverse events. Overall, it was found that radiation therapy had favorable outcome measures compared to standard of care in patients with asymptomatic high risk bone metastases.

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