Our findings until the middle of the project cannot be more exciting. We have found a novel way to systematically identify vulnerabilities in the altered brain metastasis-microenvironment that allows us to move faster in the process of discovering novel drugs to challenge brain metastasis. Interestingly this novel drug-screening platform we have called METPlatform, is fully compatible with patient-derived material and we are exploiting it in the context of a large network of hospitals nation-wide. In addition to METPlatform, we have discovered that resistance to one of the most prevalent therapies against brain metastases, radiotherapy, is originated in the microenvironment. By exploiting this finding, we have reported the first strategy to apply radiotherapy following a criterion that allows to avoid resistance either by the identification of a biomarker detectable in non-invasive liquid biopsies and/or the possibility to use a new drug that blocks resistance in those patients positive for the biomarker. In summary, our strategy will allow to personalize radiotherapy for brain metastasis for the first time, improving its efficacy and limiting unnecessary toxicities. Our findings are already in a clinical study and in a clinical trial, which confirms that by the end of the ERC project we will be able to confirm the impact of our research not only experimentally but also in cancer patients.