Relapsed/Refractory HER2+ Metastatic Breast Cancer - Episode 3

Case 1: 48-Year-Old Patient With HER2+ Metastatic Breast Cancer

Adam M. Brufsky, MD, PhD: Let’s talk about this case. This is a 48-year-old woman who presented to her primary care physician a number of years ago with a lump in her breast. She had a 4.4-cm left breast mass and 3 palpable axillary lymph nodes. Her ultrasound and mammogram confirmed these physical findings.

She was referred to a medical oncologist and had a core needle biopsy that showed ER- [estrogen receptor-negative]/PR- [progesterone receptor-negative], HER2 [human epidermal growth factor receptor 2]-positive by IHC [immunohistochemistry score] that was 3+. A CT scan of the chest, abdomen, and pelvis showed 3 liver lesions, the largest being 3.1 cm. This is the de novo patient we always talk about. She had an MRI of the brain and it was negative for metastasis. She received 6 cycles of THP [docetaxel, trastuzumab, pertuzumab], followed by HP [trastuzumab, pertuzumab] for another 12 months. That’s 18 months of therapy.

She had a partial response in her breast mass, and her liver lesions fully responded. Later, she suddenly began to have rapid unexplained weight loss. The CT scan only showed 2 new liver lesions, so not quite the symptom I would imagine. She then got a brain MRI that showed about 30 widely scattered lesions, the largest being about 0.5 or 0.6 [cm]. They have all these little punctate ones; you’ve all seen those.

The question is: what treatment would you give this person? Let’s say the brain MRI shows 3 lesions, all in the frontal cortex, with the largest being 1.5 cm. That makes it a little bit of a different question because if there are widely scattered lesions, we’re not going to want to do SRS [stereotactic radiosurgery]. We are probably going to want to do whole brain radiation. Let’s say she’s asymptomatic with no edema. The polling question is: what treatment would you recommend? T-DM1 [trastuzumab emtansine], tucatinib/trastuzumab/capecitabine, SRS to the brain metastases, clinical trial, or other.

You guys could answer that question. Let me start with Sara. How would you approach this?

Sara A. Hurvitz, MD, FACP:They’re not totally mutually exclusive, right? You could do SRS and switch systemic therapy. She is progressing systemically in the liver, so I think switching systemic therapy makes sense. I like tucatinib because it does penetrate the blood-brain barrier, but I would still be tempted and would probably talk to my radiation oncology and neurosurgery colleagues. We’d probably end up doing both the SRS and tucatinib-based therapy.

Adam M. Brufsky, MD, PhD: That’s reasonable. VK, do you have any other comments on this?

VK Gadi, MD, PhD:Yes, I agree. The tolerability of the regimen is good. You might even give this lady an opportunity to fly without SRS and have that in your back pocket. If you’re not seeing control, you can go to SRS at a later time. I don’t think there’s a wrong answer here. You could probably do it both ways.

Adam M. Brufsky, MD, PhD: Neil, do you have something to add?

Neil M. Iyengar, MD:No. She fits perfectly into the HER2CLIMB population, so I agree with everything that has been said because there is demonstrated activity of the tucatinib-based regimen in terms of CNS [central nervous system] response. Coupling that with SRS is reasonable. This is the patient we were talking about earlier with whom we would discuss foregoing local therapy to the brain. That’s a reasonable discussion here. It’s a tricky poll question because my kneejerk response would be to put her on a clinical trial. We should all be trying to prioritize clinical trials, but in the absence of that clinical availability, tucatinib plus or minus radiation is a reasonable option.

Adam M. Brufsky, MD, PhD: There’s a clinical trial that’s great; it’s not scientifically spectacular, but clinically, it’s fabulous. I believe it’s called DESTINY. In fact, I put a patient on it today with trastuzumab deruxtecan and tucatinib together. That’s a great trial that’s going to accrue quickly. If we could put as many people as we can on that, we can answer the clinical question quickly. I would agree.

I have 1 last question before we go on to the last 25 minutes and the last segment. What do you tell people about [adverse] effects? Are you seeing a lot of [adverse] effects with tucatinib? Do you have to dose reduce it at all when you give it? These are questions people who haven’t had a lot of experience with it usually ask. I’ll start with Neil. Do you see a lot of diarrhea? Do you have to dose reduce with tucatinib?

Neil M. Iyengar, MD: In my experience, this regimen is quite tolerable. We all, as oncologists, have unfortunately become very comfortable with managing diarrhea, along with oncology nursing and so forth. What I have found with the tucatinib-based regimen is that with the initiation of antidiarrheal agents, the diarrhea usually resolves or improves pretty quickly. People have to know about it and be prepared to deal with it immediately. It does come on early, usually within the first cycle.

The other consideration to keep in mind with tucatinib is that many of the [adverse] effects are likely related to capecitabine. We’re all very comfortable with managing capecitabine-related toxicity and dose modifying capecitabine as needed. We see in the HER2CLIMB data that patients in the tucatinib arm stayed on study longer and were therefore exposed to capecitabine for longer than those in the placebo arm. I think a lot of the toxicities are familiar ones that are related to capecitabine and are quite manageable.

Adam M. Brufsky, MD, PhD: Great. VK and Sara, do you have any other comments about this toxicity? Do you see any toxicity at all with this, more than you’d expect?

Sara A. Hurvitz, MD, FACP: It’s well tolerated. About 13% had grade 3/4 diarrhea. Before getting on this call, I had to dose reduce a patient on this therapy. It’s hard to tell. On the clinical trial we enrolled patients, and I had a patient on who had severe colitis, hospitalization, etc, and I was sure she was getting tucatinib. When she was unblinded after the data came out, it turned out that she wasn’t on tucatinib. She was on placebo. I completely agree that these are [adverse] effects we’re used to with capecitabine. There’s not a whole lot of difference. Tucatinib is pretty well tolerated.

VK Gadi, MD, PhD: I agree. I think the capecitabine is the real culprit. The people on the trial were actually on it for so much longer that the toxicities from capecitabine emerged ongoing on the study. That has been my experience. Something important we don’t yet have is the PRO [patient-reported outcomes] data from these studies. A lot of my colleagues, especially those in communities where patients come in from a long way away, know that this is a tremendous pill burden with this regimen. Sometimes a parenteral regimen that you’re giving every 3 weeks is better for patients. I’m curious to see what those data look like when they come out. From our perspective as physicians, this is a slam dunk and it’s easy to give, but that’s not always the perspective that matters.

Adam M. Brufsky, MD, PhD: I agree.

Sara A. Hurvitz, MD, FACP: Yes, I think the quality of life PRO data were presented at the San Antonio [Breast Cancer Symposium]. I’m trying to pull it up. I don’t have it right at my fingertips, but my recollection was that it looked fairly good, that the quality of life was maintained.

Adam M. Brufsky, MD, PhD: Right, but they’re not going to tell you that they’re struggling to take all those pills. It’s a lot.

Sara A. Hurvitz, MD, FACP: That’s true.

Adam M. Brufsky, MD, PhD: It’s about 9 pills a day, which is a lot.

Neil M. Iyengar, MD: The quality of life data are always interesting because the end point of choice is time to deterioration and whether we are avoiding that. I think that’s a fairly low bar.

Adam M. Brufsky, MD, PhD: Exactly. Women are going to do anything they can.

Transcript edited for clarity.