Ultralow-dose radiation therapy provides durable pain relief for multiple myeloma patients suffering from bone metastases while successfully preserving bone marrow status, according to prospective clinical trial data presented at the American Society for Radiation Oncology (ASTRO) meeting in Boston. Investigators found that treatment-related adverse events were minimal, allowing patients to maintain their blood counts, continue chemotherapy, and preserve options for future therapies such as transplant or CAR T-cell therapy.
Clinical Trial Results Show High Pain Response Rates
The phase II prospective clinical trial evaluated 69 patients with multiple myeloma and painful bone lesions. Participants received either a single 4-Gy radiation dose or two 2-Gy fractions, representing a sharp decrease from the conventional 30-Gy dose typically administered across 10 fractions for bone pain. At the 4-week mark, two-thirds of evaluable patients achieved a complete or partial pain response. By 6 months, that response rate climbed to 86%.
Treatment-related adverse events surfaced in only five of the 69 enrolled patients. None of these events reached grade 3 severity or higher, and none necessitated treatment interruptions or modifications. Leslie Ballas, MD, of Cedars-Sinai Medical Center in Los Angeles, presented the findings at the ASTRO conference.
Bone Marrow Preservation Enables Future Options
“The bone marrow is protected, which allows patients to get re-irradiation, maintain their blood counts, continue chemotherapy, and have room for future therapies such as transplant or CAR T-cell therapy,” Ballas stated. Because modern therapeutic agents have driven 5-year overall survival rates up to 64% for multiple myeloma patients, individuals require multiple lines of therapy throughout their lifetime and must protect their bone marrow reserves.
Data showed that the volume of bone marrow receiving 10 Gy or higher correlates strongly with hematologic adverse events. By keeping the radiation dose exceptionally low, only 19% of patients required a second course of radiation, though the possibility remains open throughout a patient’s life.
Chelsea Pinnix, MD, of the University of Texas MD Anderson Cancer Center in Houston, characterized the study as an exciting prospective phase II trial addressing a frequent complication of the disease. “The findings suggest that many patients can experience meaningful pain relief with a very low initial radiation dose,” Pinnix said. “This approach is convenient for patients, but most importantly, it provides excellent pain relief with minimal side effects.”
Investigators Set Pain Scores and Eligibility for Trial
Investigators enrolled patients with a Brief Pain Inventory score of 2 or higher who had no prior radiation therapy or surgery, no pathologic fracture in a long bone, no spinal cord compression, and no skull base or orbital index lesions. The primary endpoint measured pain response alongside daily oral morphine equivalent dose at 4 weeks.
“I think that 2 Gy times two or 4 Gy times one is, at this point, ready for clinical practice, as long as patients are appropriately counseled that it is a risk-adapted approach and that a small number of patients may need re-irradiation,” Ballas said.
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