The study, led by Ali H. Duzkalir and Selcuk Peker of Koc University Hospital in Istanbul, pooled data from twelve institutions spanning the United States, Canada, Europe, the Middle East, and East Asia. Because male breast cancer accounts for less than one percent of all breast cancer cases, and because brain metastases arise in only a subset of those patients, no single center could ever accumulate enough cases to draw meaningful conclusions. By aggregating decades of experience from flagship radiosurgery programs, including the University of Pittsburgh Medical Center, the University of Virginia, NYU Langone, Na Homolce Hospital in Prague, Taipei Veterans General Hospital, and Sheba Medical Center in Israel, the researchers assembled a cohort large enough to interrogate with modern statistical tools. Nineteen patients carrying a total of 185 individually treated lesions formed the final analytical dataset.

The technical architecture of the analysis deserves attention, because it reflects how radiosurgery outcomes are increasingly evaluated in the era of big-data oncology. Rather than treating each patient as a single independent data point, the team used generalized estimating equations with robust variance estimation, a method that correctly accounts for the fact that one patient may contribute several lesions whose outcomes are statistically correlated. Overall survival was estimated with Kaplan-Meier curves, the standard approach for handling censored follow-up times. Changes in neurological symptoms before and after treatment were tested with McNemar’s exact test, a paired analysis suited to before-and-after binary outcomes in a small cohort. To identify which radiation dose characteristics predicted treatment failure, the investigators turned to receiver operating characteristic analysis, which measures how well a continuous variable, such as tumor volume, discriminates between lesions that recur and those that do not.

The headline finding is the crude local control rate of 97.3 percent, meaning that nearly every irradiated tumor stopped growing after a single radiosurgical session. For context, brain metastases from many other cancer types often recur locally in ten to twenty percent of treated lesions even at experienced centers, so a failure rate below three percent is remarkable. The median age of the patients at the time of radiosurgery was 59.0 years, and the cohort’s median overall survival reached 28.0 months, a figure that compares favorably with published survival data for breast cancer brain metastases more broadly, where whole-brain radiation therapy cohorts frequently show far shorter survival.

Perhaps the most clinically consequential result concerns what happened outside the brain. Patients whose systemic disease, meaning cancer elsewhere in the body, was under control at the time of radiosurgery lived a median of 40.0 months, compared with just 22.0 months for those with uncontrolled systemic disease, a difference that reached statistical significance at p equals 0.032. This pattern echoes a growing body of evidence from female breast cancer cohorts, including the SYBRA study published in npj Breast Cancer in 2024, which found that systemic disease status strongly influences central nervous system outcomes after radiosurgery. The message for clinicians is unambiguous: the brain is only one battlefield, and survival in oligometastatic disease is ultimately governed by whether the cancer can be contained throughout the body.

On the dosimetric side, the study identified target volume as the single most important predictor of both treatment failure and radiation toxicity. Receiver operating characteristic analysis showed that lesion volume significantly discriminated between controlled and failed lesions, with an optimal threshold of 0.98 cubic centimeters, roughly a sphere just over a centimeter in diameter. Lesions smaller than this threshold were far more likely to be permanently controlled. The same variable independently predicted adverse radiation effects on multivariable analysis at p equals 0.013, confirming a principle well established in the radiosurgery literature: the larger the target, the harder it becomes to deliver an ablative dose without injuring adjacent brain tissue, because dose falloff is finite and larger volumes inevitably expose more normal parenchyma.

The safety and neurological data add an important human dimension. Before treatment, 63.2 percent of patients carried a neurological symptom burden attributable to their brain metastases, ranging from headaches and seizures to focal deficits. After radiosurgery, that figure fell to 26.3 percent, a statistically significant improvement at p equals 0.016. Equally important, the median Karnofsky Performance Status, a standard zero-to-one-hundred scale of functional independence used across oncology, remained stable over follow-up. In a population where brain-directed treatment can sometimes trade cognitive function for tumor control, the combination of symptom relief and preserved performance status is exactly the profile clinicians hope to see.

Why does this matter beyond the nineteen patients studied? Male breast cancer is biologically distinct in several respects. Population-based analyses of SEER registry data and recent reviews have shown that men are more often diagnosed at later stages, more frequently carry hormone receptor positive tumors, and may experience different metastatic patterns than women. Molecular studies have even documented subtype conversion in metastatic lesions, meaning the tumor’s receptor profile can shift between the primary breast tumor and its brain deposits, complicating targeted therapy. Because men are typically excluded from breast cancer trials by design or by accident, evidence for their care is often extrapolated from female cohorts. This study provides direct, lesion-level evidence that the established practice parameters for stereotactic radiosurgery, developed and refined over decades largely in women, translate safely and effectively to men.

The findings also arrive at a moment of ferment in the field of brain metastasis management. Randomized trials comparing whole-brain radiation with radiosurgery are ongoing, and the rising use of antibody-drug conjugates and other potent systemic agents has raised new questions about combined treatment toxicity, including radiation necrosis risk highlighted in a 2026 systematic review in Neurosurgical Reviews. Against that backdrop, the current study anchors one corner of the evidence base: for men with breast cancer brain metastases, focused radiosurgery achieves near-total local control, shrinks the neurological symptom burden, and preserves function, provided that lesions are kept within the volume range where the technique excels.

The authors are careful about the limitations inherent to their design. A retrospective cohort of nineteen patients cannot establish causation, cannot capture every variable that influences survival, and cannot substitute for prospective registration. The study received no external funding, was approved by the Institutional Review Board of Koc University, and was conducted in accordance with the Declaration of Helsinki, with informed consent waived due to the de-identified, retrospective nature of the data. Yet in a disease so rare that even the largest single institutions may see one case every few years, the multicenter retrospective approach is not a compromise but the only realistic path forward. The study, published as volume 179, article 73 of the Journal of Neuro-Oncology on 9 September 2026, gives clinicians treating this overlooked population something they have never had before: numbers they can stand on.

Subject of Research: Stereotactic radiosurgery outcomes for brain metastases arising from male breast cancer

Article Title: Stereotactic radiosurgery for brain metastases from male breast cancer: a multicenter retrospective study

Article References: Duzkalir, A. H., Askeroglu, M. O., Yildirim, D. C., Marciniuk, K., Bernstein, K., Tos, S. M., Reyes, J. S., Liscak, R., Simonova, G., Sumi, T., Kano, H., Kilic, T., Kilic, D., Bowden, G. N., Shemesh, S. Z., Kaisman-Elbaz, T., Lee, C.-C., Yang, H.-C., Kutuk, T., … Peker, S. (2026). Stereotactic radiosurgery for brain metastases from male breast cancer: a multicenter retrospective study. Journal of Neuro-Oncology, 179(2), Article 73. https://doi.org/10.1007/s11060-026-05795-x

Image Credits: AI Generated

DOI: 10.1007/s11060-026-05795-x

Keywords: male breast cancer, brain metastases, stereotactic radiosurgery, local control, overall survival, Gamma Knife, radiation oncology, neuro-oncology, target volume, adverse radiation effects, Karnofsky Performance Status, multicenter study