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ASCO 2017: Ado-trastuzumab Emtansine in Resistant HER2-Positive Breast Cancer

In patients whose HER2-positive metastatic breast cancer progresses on treatment with pertuzumab and trastuzumab, ado-trastuzumab emtansine (formerly T-DM1) may represent a clinically active option, according to the findings from two phase III studies. Ander Urruticoechea, MD, of Onkologikoa Foundation, San Sebastián, Spain, presented the study results in a poster session at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract 1023). Although the investigators admit their data are limited in these exploratory analyses, they conclude their findings provide additional evidence of activity with ado-trastuzumab emtansine and the real-word implications may warrant further study.

The antibody-drug conjugate ado-trastuzumab emtansine was approved in 2013 for patients with HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane. Later the combination of pertuzumab in combination with trastuzumab and docetaxel (HTP) became the first-line standard of care for this patient population.

A total of 32 of 408 patients who received HTP in the CLEOPATRA trial and 43 of 228 patients who received trastuzumab, capecitabine, and pertuzumab in the PHEREXA trial subsequently received ado-trastuzumab emtansine. The median time from discontinuing pertuzumab to beginning ado-trastuzumab emtansine was 3.5 months in those from the CLEOPATRA trial and 10.6 months in those from the PHEREXA trial. Based on their exploratory analysis of overall survival, ado-trastuzumab emtansine seemed to provide clinical activity.