image: Portrait of Professor David Krug
Credit: ESTRO / David Krug
Stockholm, Sweden: Treating breast cancer that has begun to spread around the body with targeted radiotherapy could help patients to live longer without their cancer getting worse, according to the results of a small randomised controlled trial presented at the Congress of the European Society for Radiotherapy and Oncology (ESTRO 2026) [1].
Once cancer has begun to spread within the body (metastasise) it generally becomes harder to treat and survival rates are lower. The new research focuses on patients with oligometastatic breast cancer, meaning a few small secondary tumours have broken away from the main tumour and begun to grow elsewhere in the body.
The researchers used stereotactic body radiotherapy (SBRT) to treat each small metastasis alongside usual drug treatment. This type of radiotherapy involves targeting tumours with radiation from many different angles around the body. The beams meet at the tumour delivering a very high but very precise radiation dose to the cancer cells.
Results of the trial were presented by Professor David Krug from the department of radiation oncology at University Hospital Schleswig-Holstein, Kiel, Germany. He said: “Currently, patients with oligometastatic breast cancer are usually treated in the same way as patients with more advanced breast cancer.
“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.”
The trial included 87 patients who were treated at one of 31 hospitals in Germany and Austria between March 2021 and April 2024. A larger trial was planned, but the trial was stopped early due to slow recruitment. Each patient had between one and five small secondary metastases. Half were given standard treatment, including chemotherapy and/or hormone therapy aimed at controlling the cancer as much as possible. The other half were given standard treatment as well as SBRT directed at each secondary metastasis.
Researchers monitored the patients to see whether they survived and whether their cancer continued to grow or spread. They also assessed patients’ quality of life 12 weeks after radiotherapy treatment using a standard questionnaire.
Patients who received radiotherapy targeting their secondary tumours lived without their cancer getting worse (progression free survival) for 36.2 months on average (median). This compares with 20.6 months in patients who did not receive the targeted radiotherapy. This equates to around a halving of the risk of cancer progression or death.
The quality-of-life measures were similar between the two groups with an average deterioration of around two points in a scale of 0-100 in the radiotherapy group, which was well below the pre-defined margin of ten points.
Dr Krug said: “The addition of radiotherapy directed at these small secondary tumours 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.”
However, the researchers caution that the trial is smaller than they would like. Dr Krug explained: “Recruiting patients was slower than expected and there are several possible reasons why. Many patients will have too many secondary tumours 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 randomised to standard treatment without radiotherapy, and instead asked to receive radiotherapy outside of the trial.”
Dr Krug says that further clinical trial results are needed to give a clearer picture on the effects of treating oligometastatic breast cancer with targeted radiotherapy.
ESTRO President, Professor Matthias Guckenberger, from 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 non-invasive, can usually be given over just a few treatments, and can be delivered in an out-patient 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 breast cancer patients.
“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.”
Method of Research
Randomized controlled/clinical trial
Subject of Research
People