A blood test that detects tumor DNA circulating in the bloodstream could help choose the most effective treatment options for cancer patients whose tumors have begun to spread, according to one of the largest randomized controlled trials of its kind presented at the European Society of Radiation Therapy Oncology Congress (ESTRO 2026).
The study was led by Chad Tan, Ph.D., associate professor of radiation oncology at the University of Texas MD Anderson Cancer Center in Houston, USA, and presented by Alex D. Shelley, Ph.D., assistant professor of radiation oncology at the Mayo Clinic in Rochester, USA. Also featured in today’s magazine Journal of Clinical Oncology.
This study involved a group of patients with rare metastatic cancers. This is the term used when cancer begins to spread beyond its origin. It is currently diagnosed by counting the number of metastases found on X-ray, CT, or MRI scans.
Dr Shelley told Parliament: ”Studies suggest that treating oligometastatic cancers with a combination of both chemotherapy and local treatments to the tumor site, such as precision radiotherapy, may improve cancer control. However, counting the number of lesions may not be the most effective way to identify which patients will benefit from radiotherapy.. ”
We wanted to investigate whether a new test that measures circulating tumor DNA (the part of a tumor that is shed into the bloodstream) could help us figure out which patients would benefit most from combined chemotherapy and radiotherapy, predict response to treatment, and give a more accurate long-term prognosis. ”
Dr. Chad Tang, Associate Professor of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, USA
The study included 237 patients in six subgroups with one to five metastases each: a group of patients with pancreatic cancer, one group of patients with breast cancer, one group of patients with kidney cancer, two groups of patients with prostate cancer receiving different hormone therapy schedules, and a final group of patients with other types of cancer. These patients were randomly selected to receive either drug therapy alone or a combination of drug therapy and radiation therapy.
The primary objective of the trial was to see if the combination of radiotherapy and drug therapy improved cancer control compared to drug therapy alone, which the study confirmed. But the researchers were also testing whether blood tests could be used to guide treatment.
Patients’ blood was taken at the start of the study, three months later, and again when the cancer had spread, and tested for the presence of circulating tumor DNA (ctDNA).
Sherry and Tan’s team found that patients who had tumor DNA in their blood at the start of the trial were more likely to have continued cancer growth and were more likely to die.
They also found that patients who received radiation therapy directed at sites of cancer metastasis (along with drug therapy) had improved clearance of ctDNA.
“This is important because patients whose ctDNA was removed from the bloodstream had much better outcomes and survival rates than those who did not. This supports the importance of targeted therapies, such as radiotherapy, in treating oligometastatic cancers,” explains Dr. Sherry.
The results also suggest that if circulating tumor DNA is found in the bloodstream after treatment, it may indicate that the cancer is more aggressive, that treatment has not been effective, or that there are more tumor cells that were not detected on the scan.
The researchers hope that testing ctDNA could help determine which patients are the best candidates for radiation therapy, and could also help improve treatment by telling doctors whether their cancer has changed and become resistant to current treatments.
Dr. Shelley added, “We hope that future studies will assess whether systemic therapy should be changed in these patients and whether ctDNA can be used to distinguish between which parts of the cancer are responding or resistant to treatment.”
Professor Matthias Guckenberger, chairman of ESTRO at Zurich University Hospital in Switzerland, who was not involved in the study, said: “Treatment of patients with limited spread of cancer with both drug therapy and precision radiotherapy improves their chances of survival. A growing number of studies are showing that this study is one of the largest conducted in this patient group, and suggests that adding blood tests may also allow us to more effectively monitor and target radiation therapy treatment in patients.”
“Non-invasive ctDNA marker tests support established imaging techniques, provide a more sophisticated way to see how a patient’s cancer has spread, and help doctors decide when and how to use radiation therapy to treat cancer.
“Using ctDNA as a marker may also help tailor treatment when it may not be working effectively, and provide additional reassurance when treatment is successful.”
sauce:
European Society of Radiation Therapy Oncology (ESTRO)
Reference magazines:
billboard sherryet al. (2026) Adding metastasis-directed therapy to standard of care for oligometastatic solid tumors: primary analysis of all tumor histology baskets from the phase II randomized EXTEND trial. Journal of Clinical Oncology. DOI: 10.1200/JCO-25-02856. https://ascopubs.org/doi/10.1200/JCO-25-02856
