Patrick I. Borgen, MD, chair of surgery and director of the Breast Cancer Program at Maimonides Medical Center, discussed treatment advances for HER2-positive breast cancer that occurred in 2019.
Twenty-five percent of all women with invasive breast cancer – either ductal or lobular – are found to have an amplification or abnormality in the HER2 oncogene. This is proven to be a vitally important target for therapy.
In the early 1990’s, when HER2 was first discovered, we had no therapy for it. And the chance of dying of a HER-positive breast cancer was astronomically high. Today, because our therapies have been so effective, it’s completely reversed itself. In fact, in the staging system for breast cancer, having HER2-positivity now downstages the disease. So, the big advances have been what to do in the very early breast cancer and what to do in the later-stage breast cancers.
So, in the early space there was a trial called APT, which was a phase II trial, not a phase III trial, where women with very small tumors, node-negative and HER2-positivity received a combination of chemo and trastuzumab (Herceptin), just those 2 drugs. And after 5 years, survival was so incredibly good, that that treatment, what we call TH, was adopted as therapy.
The second advance has been in the antibody drug conjugate space where patients with T2, so larger than 2 cm, HER2-positive breast cancers, who received neoadjuvant therapy do not experience a complete path response and are now treated with an antibody drug conjugate called TDM1 and the results have been really spectacular.
Those are the 2 really exciting areas to watch right now in HER2-positive breast cancer.