Adherence to HER2-Targeted Therapies in Breast Cancer

Erika P. Hamilton, MD: Let’s move on and talk about toxicities and adherence. As oncologists, that’s something we probably don’t talk about as much as we should. We talk about all this grand master data, regarding how people are responding, and then we normally have a couple of lines about adverse effects and some type of summary statement. Let’s move on and talk about that a little as well.

Stephanie Graff, MD, FACP: In the HER2 [human epidermal growth factor receptor 2]–positive space, compliance with therapy is much higher. Part of that is that it’s so in control. We know if somebody is showing up to get their trastuzumab. We know if somebody has pulled out their IV [intravenous] and is leaving before the whole dose is given. That’s never happened. We know that the medicine is being given.

When we look at trials of compliance with adjuvant endocrine therapy, we see that those numbers are lower year over year, with predictors based on age and access to medicine and health care literacy and so many different factors; in whether a patient takes it for 1, 2, 3, 5, or 10 years now. In the HER2 space, because these are mostly infusional therapies, we see much better compliance. Luckily, that’s less of a concern.

Toxicity is a concern. I’ve now had 1 patient who did not have a pathologic complete response. We started T-DM1 [trastuzumab emtansine] therapy, and the peripheral neuropathy symptoms just continued to escalate. Ultimately, we decided to drop back down to just trastuzumab. But with no data, we don’t know how to do that. However, we know that trastuzumab for a year is better than not. There are still going to be opportunities for us to be careful observers of our patients and their toxicities and modify the plan that’s in front of us.

Erika P. Hamilton, MD: Yes, absolutely. I think we’re stepping into a data-free zone. But the reality is, practicing medicine, a lot of times, is a data-free zone when you have an individual patient in front of you. I agree with you, with adjuvant T-DM1 [trastuzumab emtansine]. One of the concerns there is the length of that therapy. Although T-DM1 [trastuzumab emtansine] tends to be better tolerated than chemotherapy by itself with HER2 antibodies, a year or a prolonged amount of time can be taxing on patients. When we have somebody who isn’t tolerating that, although it’s completely data-free, dropping back and finishing a few treatments of trastuzumab, etc, is probably the most logical thing to do, as opposed to just stopping early, right?

Stephanie Graff, MD, FACP: Right, yes.

Transcript edited for clarity.