T-DM1 and AVM - Coincidence or Causation: Case Report

Background: Trastuzumab emtansine (T-DM1) is a novel agent used for the patients with human epidermal growth factor receptor (HER-2) positive breast cancer. Prolonged use of T-DM1 has been shown to cause rare adverse effects, such as hereditary haemorrhagic telangiectasia (HHT)-like symptoms and vascular malformation. The authors present a case of HHT-like symptoms and new brain arteriovenous malformation (AVM) in the setting of T-DM1 therapy for breast cancer. Observation: A 77-year-old lady with a background of metastatic breast cancer who developed HHT-like mucocutaneous clinical manifestation during treatment with T-DM1, which regressed at nine months following cessation of T-DM1. She was found to have new brain AVMs four years after commencement of T-DM1 therapy in the absence of other risk factors for AVM. Conclusion: Given the increasing use of T-DM1 for metastatic breast cancer, it is imperative for clinicians to be aware of the potential development of brain AVM whilst on T-DM1 via HHT linkage.