Case Presentation: A 56-Year-Old Woman With ER+/HER2- mBC

Virginia Kaklamani, MD: Let's move on to another case. This is a 56-year-old postmenopausal patient. She has a personal history of breast cancer; she presented with right upper quadrant abdominal pain during a routine follow-up appointment. She was diagnosed initially 8 years ago with stage 1 ER+/HER2- disease. At the time she was given adjuvant anastrozole, which she completed 3 years ago.

Now presenting with the abdominal pain, she has CT scans that are showing a liver lesion and a liver biopsy showing ER+/HER2- metastatic breast cancer. Here, the HER2 is IHC 1+. She has next-gen sequencing of the liver biopsy and it's negative for any mutations. She has a good performance status of zero.

Initially she started on fulvestrant and abemaciclib with instructions to follow up every 6 months. Now typically when we give fulvestrant and abemaciclib we follow up with all the patients monthly, at least for the first few months, then we can move on to 2 and 3 month follow ups, so typically the follow-ups are going to be a little more frequent than every 6 months.

Now, 12 months after the first line therapy, her CT scan is showing that the liver lesion has grown, and her cancer is not responsive to fulvestrant and abemaciclib. She has a liquid biopsy, and the patient is negative for any SOS1 mutation. She started on second line treatment with chemotherapy, which is paclitaxel.

So, one of the things to consider here was that she was on fulvestrant/abemaciclib, but the treatment only lasted for a year, which is a little shorter than what we would have expected from first-line endocrine therapy. That's again an indication that this tumor may be becoming endocrine resistant. So why do we decide to give paclitaxel? Taxanes are one of the most active agents we have in breast cancer in general, and so even though I probably would have given capecitabine for the reasons Elizabeth just mentioned, paclitaxel is definitely a good option at some point to give for this patient.

So, she's on paclitaxel for 12 months and then she develops a second liver lesion; she's started on doxorubicin but develops arrhythmia. Doxorubicin is another very active medication. We typically use it in the adjuvant setting, but we can use it in the metastatic setting, and it tends to offer pretty good disease control.

Now we're discussing different options with the patient. And obviously here there are other chemotherapeutic agents, but also antibody drug conjugates. So, the patient agrees to enroll in the clinical trial for sacituzumab govitecan and receives this regimen, and then at 12 months post-treatment she has stable disease, so she continues to receive benefit from this treatment. She has some mild diarrhea that's controlled with over-the-counter medications, but otherwise is doing pretty well.