On 28 September 2026, CNIO researchers reported that three drugs removed brain micrometastases in animal models before the deposits became detectable tumours. The work, from the CNIO's Brain Metastasis Group, 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 chance, not a treatment available to patients.
Published in Cancer Cell on 28 September 2026, the study 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 adjusting to their surroundings.
During that period, the cells lose some of their aggressive behaviour, but their molecular activity continues. 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, but it does not make the laboratory result 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.
Researchers also used human samples. 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.
Surgery can remove a visible brain metastasis while microscopic cancer cells remain elsewhere in the brain. Those cells may later begin growing again, causing the disease to return.
The CNIO team wants to act during the earlier pause. That would mean intervening before a lesion became visible or caused symptoms.
The research follows an earlier report on early brain spread. This study adds a more specific treatment target and a plan to remove hidden deposits. The next step is to prepare clinical trials to 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, identifying the cells at that point will be difficult.
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 whether metastatic cells can be treated before they become visible.
