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In a prospective phase II trial, ultralow-dose radiation was followed by pain responses in 66% of evaluable patients at four weeks and 86% at six months. Researchers reported few treatment-related adverse events and no adverse effect on bone marrow status; the single-arm study did not compare the approach directly with standard-dose radiation.
A prospective phase II trial found that ultralow-dose radiation was followed by meaningful relief of multiple myeloma-related bone pain, with few reported side effects and no observed adverse effect on bone marrow status. Among patients who completed pain assessments, 66% responded at four weeks and 86% at six months after either one 4-Gy treatment or two 2-Gy treatments, according to results presented by researchers at the American Society for Radiation Oncology meeting.
The study enrolled 69 people with multiple myeloma and painful bone lesions. Patients were assigned to receive either a single 4-Gy radiation treatment or two treatments of 2 Gy. Both regimens deliver a total of 4 Gy, substantially below the 30 Gy in 10 fractions described in the report as a usual regimen for bone pain. Patients with certain higher-risk conditions, including a long-bone fracture, spinal cord compression, or specified skull or orbital lesions, were not eligible.
The main outcome combined pain response and use of oral morphine-equivalent medication. A complete response meant no pain at the treated site and no increase in medication; a partial response meant pain fell by at least two points or medication use dropped by at least 25%. Response rates were 66% at four weeks among 61 questionnaire respondents, 64% at eight weeks among 47, and 86% at six months among 42. The number of respondents declined at each later assessment, so the percentages do not represent all 69 enrolled patients.
Five of 69 patients had treatment-related adverse events. None reached grade 3 or higher severity, and none required treatment interruption or modification, the investigators reported. Twelve of 63 patients, or 19%, later received additional radiation; the median time to re-irradiation was 61 days. The response rate after that further treatment was 69%. The study report said bone marrow status was not adversely affected.
Pain Relief With Marrow Preserved
Radiation can ease pain from myeloma bone lesions, but treatment planning must account for the disease’s effect on blood-forming marrow and patients’ need for ongoing cancer care. The researchers said limiting radiation exposure may leave more room for chemotherapy and future treatments, including transplant or CAR T-cell therapy. The trial’s results suggest a low-dose option may provide pain relief while preserving the ability to consider further radiation if needed.
That possibility matters as people with myeloma may receive multiple lines of treatment over time. Study presenter Leslie Ballas of Cedars-Sinai Medical Center said only 19% of patients in the trial needed re-irradiation. The result supports discussion of a risk-adapted approach, but it does not establish that low-dose treatment is best for every patient or lesion.
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Why Researchers Tested 4 Gy
Ballas said much of the earlier evidence on palliative radiation for multiple myeloma came from retrospective or observational studies. Prior prospective evidence included a randomized comparison of 30 Gy with 8 Gy, which measured pain and pain-medication use and found responses in about 80% of patients, according to the report. Those findings provide context, but they are not a direct comparison with the current trial’s 4-Gy regimens.
The study tested one 4-Gy treatment against two 2-Gy treatments, drawing on low-dose radiation experience in indolent lymphoma. Ballas said the two-fraction schedule had precedent in that disease, while a single fraction could be more convenient. In this trial, response rates were similar between the one- and two-fraction groups at the reported time points. At six months, however, the median decrease in pain score favored two fractions: 4.1 points versus 2.2 with one fraction, with a reported P value of 0.01.
“The findings suggest that many patients can experience meaningful pain relief with a very low initial radiation dose.”
— Chelsea Pinnix, MD, University of Texas MD Anderson Cancer Center and ASTRO expert
Limits of the Trial Evidence
The trial was single-arm in its overall design and compared two ways of delivering the same 4-Gy total dose, not low-dose treatment against standard-dose radiation or no radiation. The investigators compared outcomes with historical evidence, which cannot provide the same direct comparison as a randomized trial against another dose strategy.
Follow-up questionnaires were available for fewer patients at each later time point, and the six-month response rate was calculated from 42 responses. The report does not establish how results would differ across specific lesion locations or patient groups, nor does it show whether the approach improves longer-term disease outcomes. Researchers also reported a lower median pain-score decrease with one fraction than with two at six months, despite broadly similar response rates. The reasons for that difference and its clinical importance remain unclear.
Use in Myeloma Care
Ballas said at the meeting that she believes the two 2-Gy treatments or single 4-Gy treatment are ready for clinical practice when patients are appropriately counseled about the possibility of re-irradiation. ASTRO expert Pinnix said the findings may lead clinicians to consider radiation earlier for painful myeloma bone disease. These are expert views based on the presented study, not a report of a newly issued treatment guideline.
For now, clinicians will need to weigh pain, lesion characteristics, marrow considerations, and other planned myeloma therapies when selecting radiation. The presented results extend through six months; the report does not specify a longer follow-up milestone or a planned direct comparison with standard-dose treatment.
Key Questions
What radiation schedules did the trial test?
Patients received either one 4-Gy treatment or two treatments of 2 Gy each, for a total dose of 4 Gy in both groups.
How many patients had a pain response?
Responses were reported in 66% at four weeks, based on 61 completed questionnaires, and 86% at six months, based on 42. The later percentage reflects respondents, not all 69 people enrolled.
Did patients need more radiation?
Twelve of 63 patients, or 19%, received re-irradiation. The median time to another course was 61 days, and the reported response rate after re-irradiation was 69%.
Did the trial prove low-dose radiation is better than standard treatment?
No. The study compared two schedules with the same 4-Gy total dose and did not directly compare them with standard-dose radiation. Its single-arm phase II results cannot establish superiority.
What did researchers report about side effects and bone marrow?
Five of 69 patients had treatment-related adverse events; none were grade 3 or higher or led to treatment changes. Researchers reported no adverse effect on bone marrow status in the study.
Source: rss
