This observation suggests that the combination of trastuzumab and paclitaxel is less active in controlling brain metastases, especially in patients with osimertinib as last treatment, an EGFR TKI with excellent CNS penetration and efficacy.3,34 The cause for this might be a sudden loss of tumour control in the brain, caused by osimertinib discontinuation and the limited CNS bioavailability of trastuzumab and paclitaxel due to the blood–brain barrier. The gene discussed is EGFR; the disease is neoplasm.