Her-2 positive breast cancers depend on the growth protein Her2 for continued cancer growth. We have a few different treatments that can “turn off” this Her-2 growth protein. Frequently, we will use a combination of chemotherapy and Her-2 targeted medicine prior to surgery in Her-2 positive breast cancer patients. The goal is to get rid of the tumor prior to surgery. About 50% of the time at surgery, there will still be tumor left after chemotherapy. The Katherine trial was designed to look at these patients who did not achieve a complete response to “neoadjuvant chemotherapy” (chemotherapy prior to surgery). These patients were randomized to either receive the Her2 targeted drug, trastuzumab, that they received with chemotherapy, or a newer Her-2 targeted drug, Kadcyla, to complete a year of treatment. Kadcyla combines a chemo to a Her-2 linking drug to help better facilitate a “targeted kill” of cancer cells.
The results showed that switching to Kadcyla post-op in these Her-2 + breast cancer patients cut the risk of recurrence by 50%. We are eagerly awaiting FDA approval for this indication so that we can use Kadcyla in patients who were treated with Her-2 combination chemotherapy prior to surgery but still had tumor left at the time of surgery.