Trastuzumab-emtansine induced pleural and pericardial effusions.

INTRODUCTION: Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate which combine trastuzumab (T), a monoclonal antibody targeting the human epidermal growth factor receptor-2 (HER2), and a cytotoxic molecule derived from maytansine (DM1). CASE REPORT: We report the first case of T-DM1-associated pleural and pericardial effusions three weeks after the second course of T-DM1 in a patient with breast cancer. Drug-induced pleural and pericardial effusions was implicated in the absence of other etiologies. The Naranjo Scale indicated a probable drug-induced adverse reaction.Management & outcome: The patient fully recovered after thoracentesis and discontinuation of T-DM1. The patient has reported no side effect after the sixth course of trastuzumab. DISCUSSION: To our knowledge, this is the first case in the literature of bilateral pleural and pericardial effusions in a patient treated with T-DM1. The successful initiation of treatment with trastuzumab following withdrawal of T-DM1 suggests that emtansine played a role in the development of bilateral pleural and pericardial effusions. We hypothesize that the patient's condition was a result of a local inflammatory reaction to emtansine by direct toxicity.