Molecular Pathology Laboratory Network

Retesting patients with metastatic breast cancer (MBC) for over-expressed HER2 status could predict effectiveness of trastuzumab-DM1 (T-DM1), according to researchers who presented a poster at the 2010 American Society of Clinical Oncology meeting.

In a retrospective analysis, researchers scrutinized paraffin-embedded tissue samples from 222 patients treated in two phase II studies that evaluated the effectiveness of T-DM1, a novel anti-HER2 antibody-drug conjugate containing trastuzumab (Herceptin) and DM1, a derivative of the anti-microtubule agent maytansine.

HER2 overexpression was associated with a longer progression-free survival, with the median progression-free survival reaching 12.32 months in patients with overexpressing tumors and a median of 2.17 months among patients with normal HER2 expression.

The antibody-drug conjugate T-DM1 showed encouraging efficacy for patients with HER2-positive (HER2+) MBC who had progressed on prior HER2-directed therapies, according to researchers. HER2+ status by central retesting also correlated with better responses to T-DM1. Therefore, T-DM1 "is beginning to stand out as a treatment for women who have been heavily pretreated for metastatic breast cancer."

For more information about identifying HER2 status by immunohistochemistry and fluorescence in situ hybridization (FISH) technologies, contact a technical service specialist at MPLN.