ER+ Early Breast Cancer Future Directions and A Note on Ki-67 Analyses

EP: 1.Introduction: A 54-Year-Old Woman With ER+/PR+ Breast Cancer

EP: 2.Adjuvant Therapy Options for HR+ Breast Cancer

EP: 3.CDK4/6 Inhibitor Breast Cancer Clinical Trials

EP: 4.Common Adverse Events With CDK4/6 Inhibitors

EP: 5.Case Patient Prognosis

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EP: 6.ER+ Early Breast Cancer Future Directions and A Note on Ki-67 Analyses

Lowell Hart, MD, FACP: Well, it is a very exciting time for women [with] both early and advanced hormone receptor-positive breast cancer. From the days of just having tamoxifen and the emergence of the aromatase inhibitors, things have changed greatly.

The availability of the CDK4/6 inhibitors has been an amazing breakthrough for many, many women with advanced disease, and I am very excited that now at least 1, and possibly eventually more than 1, may become available for use in the primary care setting, too.

I’ve said for many years, when these drugs came out for metastatic breast cancer, that it’s a shame we couldn’t figure out how to use them in early-stage disease because I was convinced that we would cure more women with the most common type of breast cancer that we see.

Now we’re starting to see that. Thank goodness. I was very excited when the monarchE results came out and look forward to being able to give many more women, especially these women with these high-risk features, a much better chance of remaining free of cancer. That’s exciting.

There also are a lot of other new drugs, oral SERDs [selective estrogen receptor degraders] or oral drugs, which would work similarly or perhaps even better than fulvestrant [Faslodex] in an oral formulation or on the horizon and may come out sometime in the next year or 2, hopefully so.

There’s a lot of very interesting other ways that people are looking to interfere with this hormone receptor pathway that drives so much of the breast cancer that we see. The average patient with breast cancer, I’d say two-thirds or three-quarters of them, are going to have hormone receptors so it’s a very, very, excellent target and has been for many years.

It is exciting to see now that we’re getting more nuanced in how we can attack this and that we’re adding on other means of strengthening our hormonal attack on these patients with both early and advanced disease. It’s an exciting time.

It’s important for oncologists to know this in the early stage setting that they need to speak with the pathologists which we have at our institution now about this Ki-67 assay because the approval of abemaciclib [Verzenio] was with a companion diagnostic from 1 laboratory that does Ki-67s and does them in a standardized manner.

One of the criticisms of Ki-67 testing in the past and the reason that it has not in general become standard throughout the world is because it does have some subjectivity in the analysis of it so the results from 1 lab aren’t completely comparable to those from another lab.

It is important since abemaciclib is not an inexpensive drug and we certainly want to make sure that it is covered by insurance carriers for any patient who can benefit from it to get the testing done appropriately.

You can’t just necessarily expect that an insurance company will cover it for any old lab that is going to give you a Ki-67 result. This is really just emerging now, so this is something the doctors and the pathologists that they work with, oncologists, and their pathologists are going to have to be aware of.

Really, this has just been coming about since the fall of 2021 so everyone’s getting used to this now and whether physicians who are in an academic or a private practice setting, we’re all kind of working with this now and trying to work through this, but it is important for people to be aware of the nuances of Ki-67 testing. That it’s not just the same thing as sending a CDC [complete blood count] on a patient.

This transcript has been edited for clarity.

Case: A 54-Year-Old Woman with ER+/PR+ Breast Cancer

Initial Presentation

• A 54-year-old, postmenopausal woman presents with a newly diagnosed lump in her right breast
• She has no family history of cancer and underwent menopause at age 50

Clinical work-up

• Imaging demonstrated a 2.4-cm solid mass in the right upper quadrant with no suspicious lymphadenopathy identified
• Core biopsy: positive for invasive ductal carcinoma, ER 100%, PR 97%; HER2 1+ and FISH negative; Ki-67 45%; modified Bloom-Richardson grade 3
• Lumpectomy and sentinel lymph node biopsy performed
  • Tumor size is 2.4 cm, and 3 LNs are positive for metastatic disease
• 21-gene assay recurrence score is 30
• pT2N1M0, stage IIB
• ECOG PS is 0

Treatment

• Patient underwent partial mastectomy with no residual disease
• She is given radiation therapy to intact breast
• She is started on adjuvant chemotherapy with cyclophosphamide and docetaxel

Followed by adjuvant therapy with AI + 2 years of abemaciclib