Researchers at Mayo Clinic have reported clinical outcomes from the first series of patients with superficial malignancies treated with minibeam radiation therapy (MBRT), providing early clinical evidence for an approach that uses spatially separated, submillimeter radiation beams.
The study, Clinical Outcomes of Minibeam Radiotherapy for Superficial Skin and Soft Tissue Malignancies, was published online on August 14, 2026, in the International Journal of Radiation Oncology, Biology, Physics. The study was led by Kiran K. Chauhan.
MBRT is a spatially fractionated radiation technique that creates alternating regions of high radiation dose, known as “peaks,” and substantially lower-dose “valleys.” In the Mayo Clinic implementation, 0.5-mm-wide beams were separated by 1.1 mm center-to-center using a tungsten collimator and a clinical orthovoltage radiation system.
Mayo Clinic previously reported the first clinical implementation of MBRT in two patients in 2024, demonstrating that the technique could be delivered clinically while maintaining distinct peak-and-valley dose distributions (DOI: 10.1016/j.ijrobp.2024.06.035 ). The new study expands that initial experience into the first clinical series evaluating outcomes in patients with superficial skin and soft tissue malignancies.
Between December 2023 and May 2025, 36 patients with 46 lesions were treated with MBRT. The population was heavily pretreated: 90% of patients had received at least two previous systemic therapy regimens, and 43% of lesions had previously received radiation therapy. Most lesions, 39 of 46, were treated with MBRT alone. Median follow-up was 15.1 months.
Clinical Outcomes
Symptomatic improvement, including improvements such as pain relief, tumor shrinkage, or hemostasis, was documented in 86% of patients.
Among 40 lesions evaluable for response:
- 22.5% achieved a complete response
- 25.0% achieved a partial response
- 45.0% had stable disease
At 12 months, the cumulative incidence of local progression was 11.1% across all 46 lesions and 7.7% among lesions treated with MBRT alone.
Treatment-related skin toxicity was predominantly mild. Grade 1 dermatitis occurred in 58% of patients and one patient experienced grade 2 dermatitis. Two other grade 3 adverse events, persistent ulceration and necrosis, were reported, while no grade 4 or 5 toxicities occurred.
Sean S. Park, MD, PhD, Professor of Radiation Oncology and radiation oncologist at Mayo Clinic, described the work on LinkedIn as an important milestone in translating MBRT from preclinical research into patient treatment.
He wrote:
“It represents an important first step in evaluating whether this approach can maintain effective treatment while better sparing normal tissue.”
Park also highlighted the multidisciplinary effort required to move the approach from preclinical research into patient care and expressed gratitude to the patients who made the work possible.
While the findings show encouraging early local control, symptomatic improvement and tolerability, the evidence comes from a single-institution clinical series without a conventional-radiotherapy comparator. Further prospective investigation will therefore be needed to establish the safety, efficacy and potential normal-tissue-sparing advantages of MBRT.
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