Ado-Trastuzumab Emtansine-Induced Pulmonary Toxicity: A Single-Institution Retrospective Review

T-DM1 is an antibody drug conjugate with proven efficacy in metastatic breast cancer for progressive disease refractory to trastuzumab. Drug-induced pneumonitis is a rare serious potential adverse effect. The purpose of this review was to estimate the incidence of pulmonary toxicity at our institution.

A retrospective analysis of electronic medical record data inclusive of all women and men aged 18 years and older treated with T-DM1 at out institution was undertaken. The records were reviewed for clinical symptoms and/or radiographic evidence concerning for pneumonitis. We identified variables of interest with regard to potential risk factors for toxicity.

A total of 50 patients were included, 6 (12$) of whom had radiographic and/or clinical symptoms concerning for T-DM1-induced pneumonitis. All 6 patients had metastatic or unresectable breast cancer. Of the 6 patients, 5 (83$) had suspected pulmonary metastases, 1 (17$) had a history of underlying lung disease, and 5 (83$) had a history of prior taxane therapy. Pulmonary metastases (p = 0.38), the median number of treatment cycles (p = 0.29), prior taxane therapy (p = 0.99), underlying lung disease (p = 0.99), and hormone receptor positivity (p = 0.66) did not have any statistical significance for an association with pneumonitis.

Pneumonitis is a recognized toxic effect of T-DM1. While our sample size was small, the number of events was higher than described in the literature, which may be an artifact of referral bias. Future studies with a larger sample population may detect potential risk factors for toxicity.