Ultra-Low-Dose Radiotherapy Relieves Myeloma Bone Pain in Trial

Multiple myeloma is a cancer of plasma cells in the bone marrow that commonly causes painful bone lesions. These lesions can lead to fractures, impaired function, and reduced quality of life. Radiation therapy is often used for symptom control, but referral may be delayed because of concerns about bone marrow exposure and treatment coordination. New findings now show that ultra-low-dose radiation therapy can relieve uncomplicated bone pain while limiting toxicity.

Tthe multi-institutional phase II trial involved investigators from Cedars-Sinai (Los Angeles, CA, USA) and enrolled patients at seven institutions. The approach used 4 Gy of radiation, delivered either as a single 4 Gy treatment or as two treatments of 2 Gy each. Eligible patients had painful bone lesions without spinal cord compression, pathologic fracture of a long bone, or other urgent complications. The strategy was designed to provide pain relief while preserving bone marrow and the option for additional radiation if needed.

Researchers assessed 63 evaluable patients at four weeks, eight weeks, and six months. Pain response was measured with patient-reported Brief Pain Inventory scores and oral morphine equivalent dosing, using international consensus criteria for palliative radiation therapy. The primary endpoint was patient-reported pain response at four weeks. Patients without adequate pain control could receive additional radiation therapy beginning four weeks after the initial course.

Pain reduction was reported by 66% of patients at four weeks, 64% at eight weeks, and 86% at six months among those who completed questionnaires. The median time to pain relief was 36 days, and the median duration of relief was 148 days. Outcomes were similar whether radiation was delivered in one session or two. Overall, 19% of patients received a second course of radiation to the same site at a median of 71 days, and the pain response rate after reirradiation was 63% at four weeks.

Adverse effects were limited and mild. Four patients experienced grade 1–2 fatigue, and one patient reported mild radiation-related skin changes. Results were presented at the American Society for Radiation Oncology (ASTRO) Annual Meeting. The findings also suggest that shorter radiation courses may be easier to integrate with systemic therapy for patients who may develop multiple painful lesions over time.

“My hope is that these findings will help more multiple myeloma patients get pain relief more quickly. Even though this is a relatively small study, we now have prospective data from multiple institutions showing that this approach can provide meaningful pain relief with minimal side effects, making it a practical and flexible strategy for routine clinical care,” said Leslie Ballas, MD, FASTRO, principal investigator of the trial and a professor of radiation oncology at Cedars-Sinai in Los Angeles.

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