Spanish researchers have discovered a brief vulnerable stage in brain metastasis — and shown that three drugs can wipe out the microscopic cancer seeds before they grow.

The CNIO team, led by Manuel Valiente, found that metastatic cells entering the brain go through a “proliferative pause”, temporarily abandoning aggressive behaviour to adapt to their new environment. Two of the three drugs that killed them are already approved for other uses.

Published in Cancer Cell on September 28, the six-year study involved over 70 authors from 20 institutions across five countries, and the findings were validated in human tissue samples.

The discovery opens a possible strategy to prevent cancer returning after surgery — and to attack metastasis before it causes symptoms, a long-standing goal in oncology.

The catch: no test can currently detect these micrometastases. The team is now hunting for biomarkers to identify at-risk patients.

“This is the beginning of the race to prevent metastasis,” Valiente said. Clinical trials are the medium-term goal.