Local radiotherapy may help control disease spread in patients with oligometastatic breast cancer, according to findings from the OLIGOMA trial presented during the Congress of the European Society for Radiotherapy and Oncology (ESTRO 2026; Abstract 5611).
“Currently, patients with oligometastatic breast cancer are usually treated in the same way as patients with more advanced breast cancer,” said David Krug, MD, Professor in the Department of Radiation Oncology at University Hospital Schleswig-Holstein, Kiel, Germany. “Although we know that stereotactic body radiotherapy is a very effective tool in cancer generally, its use in patients with oligometastatic breast cancer has been limited due to a lack of research that proves any benefit beyond a local treatment effect. This means that it might shrink or slow the growth of the secondary tumour being targeted, but there’s been no evidence that it improves overall progression-free survival.”
Background and Study Methods
Stereotactic radiotherapy has been suggested to improve outcomes in patients with oligometastatic disease, but it had not previously been proven for patients with oligometastatic breast cancer.
Investigators conducted a randomized, controlled, multinational, multicenter study called OLIGOMA to explore the efficacy and tolerability of local radiation therapy in patients with oligometastatic breast cancer. Patients were eligible if they had breast cancer with up to five metastases and if they were eligible for palliative systemic drug therapy.
The participants were randomly assigned (1:1) to either the control group to receive drug therapy alone or palliative radiation, or the experimental group to receive additional local therapy, preferably local radiotherapy.
Co-primary endpoints were progression-free survival and quality of life at 12 weeks after randomization.
However, the study was terminated early in June 2025 as a result of slow recruitment. “Recruiting patients was slower than expected and there are several possible reasons why. Many patients will have too many secondary tumors by the time cancer spread has been detected, so this treatment would not be suitable for them. We also found that patients often wanted to receive radiotherapy, having heard about its potential benefits. They were not willing to take part in the trial knowing that they might be randomized to standard treatment without radiotherapy, and instead asked to receive radiotherapy outside of the trial.”
Key Findings
A total of 87 patients from Germany and Austria were enrolled in the study prior to it closing early. Thirty-nine patients experienced disease progression or death.
The median progression-free survival was 20.6 months (95% confidence interval [CI] = 12.5–28.6) in the control group and 36.2 months (95% CI = 24.3 to not determinable) in the experimental group (hazard ratio [HR] = 0.48; 95% CI = 0.25–0.92; P = .022).
In terms of health-related quality of life, the mean difference from baseline was –2.1 points (95% CI = –9.2 to 5.1), which demonstrated noninferiority.
“The addition of radiotherapy directed at these small secondary tumors meant that, on average, patients lived for longer without their cancer getting worse. It’s also important that there was no major effect on patient’s quality of life,” Dr. Krug said.
ESTRO President, Matthias Guckenberger, MD, Chairman of the Department of Radiation Oncology at the University Hospital Zurich, Switzerland, who was not involved in the research said, “Stereotactic body radiation therapy is a very precise treatment that works to destroy cancer cells while protecting the rest of the body. It is noninvasive, can usually be given over just a few treatments, and can be delivered in an outpatient setting. For patients, this can mean more effective cancer treatment, a lower risk of side effects, and being able to live a more normal life.”
“Whereas focused radiotherapy for oligometastatic cancer is well established for other cancer types, such as prostate cancer or lung cancer, prior experiences in breast cancer trials have been disappointing. This study, despite being small and not concluding, gives new hope for our [patients with] breast cancer,” Dr. Guckenberger added. “Results from further trials are expected in the coming years. In the meantime, this treatment may be considered on an individual basis after thorough discussion between a patient and their doctor.”
DISCLOSURES: Funding for this study was provided by Deutsche Krebshilfe (German Cancer Aid). For full disclosures of the study authors, visit estro.org.
