CNIO researchers found a short stage when early brain metastases are unusually vulnerable. Three drugs removed micrometastases in animal models before they developed into detectable tumours.
On 28 September 2026, CNIO researchers reported that three drugs removed brain micrometastases in animal models before the deposits became detectable tumours. The work came from the CNIO's Brain Metastasis Group. It points to a narrow biological stage when cancer cells are unusually exposed.
The result could eventually support treatment after surgery to reduce the risk of relapse. It is not a diagnostic test. No biomarker can currently detect micrometastases, so this remains a research opportunity rather than a treatment available to patients.
The British PEACE consortium contributed samples obtained through autopsies, allowing researchers to study microscopic metastatic deposits that are generally too small to detect in living patients with standard imaging.
The study was published in Cancer Cell on 28 September 2026. It examined what happens when metastatic cells first settle in a new organ. Some do not start multiplying at once. They enter a short pause while they adjust to their surroundings.
During that period, the cells lose some of their aggressive behaviour. Their molecular activity does not stop. That creates a possible point of attack. MedicalXpress described this early adaptation phase as the study's central discovery.
Researchers led by Manuel Valiente, head of CNIO's Brain Metastasis Group, tested three drugs in animal models. The combination removed micrometastases before they formed detectable lesions. Two of the drugs are already approved for other indications.
That could make clinical testing easier to plan. It does not turn the laboratory result into a proven preventive treatment.
The project lasted about six years. More than 70 co-authors from roughly 20 institutions in Spain, the United Kingdom, Germany, France and the United States took part.
Human samples were also used. The British PEACE consortium supplied post-mortem material, while Spain's National Brain Metastasis Network, known as RENACER, provided samples from living patients. Valiente created RENACER in 2021.
The project took about six years and involved researchers from around 20 institutions across five countries. Reports emphasize that the vulnerable phase is very short and biologically limited, making it difficult to target without molecular markers that identify the cells during this early state.
The medical problem is specific. Surgery can remove a visible brain metastasis while microscopic cancer cells remain elsewhere in the brain. Those cells may later begin growing again. The disease can then return.
The CNIO team wants to act during the earlier pause. Waiting for a lesion to become visible or cause symptoms would come later.
The research follows an earlier report on early brain spread. This study adds a more specific treatment target and a plan for removing hidden deposits. The next step is to prepare clinical trials that can test the approach in patients.
Researchers also need biomarkers that can find micrometastases despite current limits in detection. The vulnerable phase is very short and biologically limited. Without molecular markers, it will be difficult to identify the cells at that point.
The finding has a clear limit. Brain metastasis prevention has not been achieved. The CNIO work gives researchers a defined target before conventional scans can reveal the disease, but diagnosis and clinical testing still stand between animal models and patient care.
For now, the practical question is simple. Can metastatic cells be treated before they become visible?
