An Introduction to Breast Cancer Therapies: A Patient Resource From Samuel Kareff, MD, MPH

Oncology Data Advisor: Welcome to Oncology Data Advisor. Today I'm here with Dr. Samuel Kareff, who is a Hematology-Oncology Fellow at the University of Miami's Sylvester Comprehensive Cancer Center. Dr. Kareff, thank you for joining today.

Samuel Kareff, MD: Thanks so much for having me, Keira.

Oncology Data Advisor: Definitely. Would you like to tell us a little bit about yourself and your research?

Dr. Kareff: Sure. I'm a Clinical Fellow here at the University of Miami's Sylvester Comprehensive Cancer Center, along with Jackson Memorial Hospital in Miami, Florida. As a Clinical Fellow, I am being trained in the care and management of folks with all types of both solid and liquid tumors, so both hematology and oncology. In that capacity, I see patients all around here in my native South Florida area, and I also engage in research, especially in solid tumors. The majority of my research has to do with lung and breast cancers.

Oncology Data Advisor: Great. What would you like to tell us today about the overview of breast cancer and its treatments?

Dr. Kareff: Sure, and I really appreciate the invite. I think this is a very important month, being Breast Cancer Awareness Month. The goal of this discussion today is to help patients who may have newly diagnosed breast cancer or who may have a recurrence of their old breast cancer and are looking to discuss treatment options with their oncology team.

I'll go ahead and get right into it. As most folks with cancer unfortunately know, cancer is practiced in a team-based model. There are three major medical teams that participate in care of patients with cancer. Those are surgical oncologists, radiation oncologists, and medical oncologists, of which I'm a member of the latter group. I won't be touching too much on the approaches using radiation therapy engaged by the radiation oncologists, or surgical therapies, with procedures like mastectomies and those sort of things with our surgical oncologists. But these are important treatment approaches that need to be discussed with those respective specialists whenever any patient is diagnosed with breast cancer.

To talk a little bit about what we can offer folks with breast cancer from the medical oncology side, I thought we could briefly discuss five major groups of treatment strategies that we routinely employ in our breast cancer clinics. Now, a lot of these treatments have to do with each patient's specific type of cancer and the type of receptors or proteins that the cancer expresses. These are very important to understand and discuss in detail with your medical oncologist, because through these informed decisions, you'll be able to understand why you're being prescribed certain types of medications and not other ones.

Without further ado, let's go ahead and discuss five major types of treatment strategies that we have in the treatment of breast cancer. The first and maybe most common treatment strategy that's employed in breast cancer from medical oncology is related to hormone therapy. You might have heard this a lot in the media and that sort of thing, so let's briefly discuss this. A lot of breast cancers will express proteins that relate to hormones in the body, specifically estrogen and progesterone. These are also known as ER, meaning estrogen receptor, and PR, meaning progesterone receptor. If your type of breast cancer expresses these proteins, you may be eligible for hormone therapy, which basically acts to block the effects of either estrogen or the receptor on the breast cancer cells from multiplying and growing.

There are several types of hormone therapies, but two of the most common types you'll hear relate to blocking estrogen. You may have heard of a drug called tamoxifen—this is a selective estrogen receptor modulator—or you might have heard of a drug like anastrozole, an aromatase inhibitor. As I mentioned, with a long discussion with your medical oncologist, you can decide which of these drugs may be appropriate for you, depending on your age, if you're planning on having children, and what other medical issues and side effects you may have experienced in the past. There's certainly something to keep in mind when discussing hormone therapy.

The second group of medicines that we'll be talking about today relates to antibody therapy. Many of you may have heard of a receptor called human epidermal growth factor receptor 2 (HER2). This is formally known as ERBB2. This HER2 receptor, just like the previous group we described, can also be expressed on breast cancer cells. When it's described in high enough quantities, it may be eligible for treatment with an antibody therapy that attacks this receptor, the HER2 receptor. You may have heard of drugs like trastuzumab or pertuzumab for this sort of treatment. Again, you'll have to have a discussion with your oncologist, because even if a breast cancer cell has a little bit of HER2, it may or may not qualify for these sorts of treatments depending on your disease stage and other factors going on in the care of your cancer. It's certainly something worth noting.

The next treatment we'll talk about today is targeted therapies. These sorts of therapies rely on the genetic information that either your breast cancer cells or your body's normal cells may express, either within the cells themselves or at baseline. Let me dive a little bit into this, because this might be the first time you're hearing more about these genetic changes that might qualify you for targeted therapy. When we're born, we inherit half a set of our genes from each of our birth parents. If we received certain sorts of genetic mutations at birth, or what we call germline mutations, you may express these mutations in all of your cells, including those in the breast cancer cells.

If you have a germline genetic mutation in a gene like BRCA1 or BRCA2, you may be eligible for specific drugs that target this genetic mutation, such as the poly-(ADP) ribose polymerase (PARP) inhibitors. You may have heard of a drug like olaparib. Again, it depends upon what stage your breast cancer may be in and what your family history is that may make you eligible or ineligible to be tested for this sort of genetic mutation, and this is something worth exploring with your medical oncologist in detail.

So that's on one end of the spectrum. On the other end of the spectrum might be what we call somatic mutations, meaning the mutations we aren't born with, but either our cancer cells or sometimes even our normal cells might develop over the course of life with other sorts of pollutions, exposures, and that sort of thing. One of the common genes that we can test the cancer cells for specifically is called PIK3CA. If your cancer cell expresses this gene mutation, it's possible you may be eligible for a targeted therapy called alpelisib. Again, this would need to be given in combination with other therapies, and it depends on the genetic results of your own testing. It's certainly something worth discussing with your oncologist, as I mentioned earlier.

The fourth group we'll talk about today is immunotherapy. This is a very exciting field in medical oncology, and it's made really great treatment advances in the past 10 to 20 years. There's specifically a protein that's expressed on the tumor cells, and around the tumor cells, called PD-L1, which stands for programmed death ligand-1. It's a complicated name, but a simple subject. If your cancer center cells or the tumor around your cancer cells expresses this PD-L1, you may possibly be a candidate for immunotherapies that target this protein specifically. One example of this would be pembrolizumab. It's certainly something worth addressing with the oncologist because these drugs have very specific sorts of side effects, and you'd need to make sure you don't have any other medical conditions that would withdraw your candidacy from this treatment.

The last category I'll talk about today is chemotherapy. This is probably the longest tradition of targeted drugs we have in medical oncology. Even though they are the oldest, they certainly are used every single day in the cancer clinic, especially in the treatment of breast cancer. Now, we're just discussing the basics of these treatments today, so I won't go into a lot of the details of these. You might've heard of drugs like doxorubicin, cyclophosphamide, and paclitaxel, as these are often used in the treatment of breast cancer. Each of these drugs has very specific side effects that have been studied for decades, so you will definitely engage in long discussions with your oncologist prior to starting these drugs and consenting to their use. But they're something you might have read about on the internet, so it's nice to get a little bit of information before you enter the exam room, so you can be informed about the discussion.

Now, I would be remiss not to mention a unique set of drugs, the antibody-drug conjugates, because these have recently made great research and treatment advances in this setting of breast cancer. These were actually discussed and given a standing ovation at our recent oncology meeting in June of this year. Basically, this combines the ideas of the antibody therapy we talked about earlier along with chemotherapy. One drug that you might have seen in the news recently is called trastuzumab deruxtecan. This is one that will be increasingly used in the oncology clinic, as well. A lot of the principles we've discussed already are the same for this drug class. Again, it's just something you want to keep an eye on should your oncologist decide to prescribe these drugs for you.

That was certainly a lot of information to discuss about these big five drug classes in the treatment of breast cancer. The goal of this was just to give you a little bit of knowledge and empowerment before you enter the examination room with your medical oncologist. These topics are something that you will certainly address in greater detail when you meet with your oncologist to begin or to restart your breast cancer treatment.

About Dr. Kareff

Samuel Kareff, MD, MPH, is a Medical Oncologist and a Hematology-Oncology Fellow at the University of Miami's Sylvester Comprehensive Cancer Center, and Jackson Memorial Hospital in Florida. He has special research interests in health advocacy, public policy, and the development of cancer therapies.

Transcript edited for clarity. Any views expressed above are the speaker's own and do not necessarily reflect those of Oncology Data Advisor.