Efficacy of T-DM1 for leptomeningeal and brain metastases in a HER2 positive metastatic breast cancer patient: new directions for systemic therapy - a case report and literature review

BACKGROUND: Herein, we report a complete response after whole brain radiotherapy (WBRT) and concomitant T-DM1 in a patient with HER2-positive metastatic breast cancer (MBC) and extensive brain and leptomeningeal involvement. CASE PRESENTATION: A 46 years old Caucasian woman with HER2-positive MBC and no baseline CNS involvement, started in August 2015 1(st) line therapy with Pertuzumab-Trastuzumab-Docetaxel, with partial response. However, in April 2016 the patient eventually progressed with emergence of brain and leptomeningeal metastases. Hence, she started in May 2016 2(nd) line therapy with T-DM1 and concomitant WBRT, with complete response (CR) after 3 courses of therapy, with complete resolution of neurological symptoms and no relevant toxicities. The CR is lasting over 13 months and the patient is out of corticosteroid use. CONCLUSIONS: To the best of our knowledge, this is the first case reporting interesting antitumor activity of T-DM1 and concomitant WBRT in both brain and leptomeningeal metastases, with a favorable safety profile and prolonged extracranial disease control. Further prospective studies should confirm these findings.