CDK 4/6 inhibitor side effects, treatment length, and more
Dr. Pooja Advani is a breast oncologist and the Director of the Robert and Monica Jacoby Center for Breast Health at Mayo Clinic, Jacksonville. In a recent interview, we asked Dr. Advani about CDK4/6 inhibitors and how they can support patients with hormone receptor-positive, HER2-negative, metastatic breast cancer.
Watch the full interview and uncover how you can monitor treatment effectiveness, below.
Keep reading for key questions from the interview.
The following questions and responses have been lightly edited for grammatical purposes.
1) What are CDK 4/6 inhibitors and how do they work in cancer treatment?
CDK 4/6 are proteins that are involved in the regulation of the cell cycle. They make sure that cell cycles are orderly and that cell division is taking place in a regulated manner. This process is disrupted in a cancer cell. CDK 4/6 inhibitors, which essentially are blockers, help restore this check and balance system that the cancer cell has disrupted and allows the cancerous cell to be killed.
It’s approved in combination with endocrine therapy, which are hormone-blocking agents for the management of patients with metastatic (which is Stage IV), hormone receptor-positive, HER2-negative breast cancer at this time.
2) What are the most common side effects of CDK 4/6 inhibitors?
When we think about CDK 4/6 inhibitors, there are three different medications approved in this family or this class. They tend to have slightly different side effects. The way I discuss with patients is that you have three family members. Just like all family members are not the same, you have slightly different side effects with each of them.
In general, the side effects can include things such as fatigue, tiredness, or changes in the blood counts, particularly to the white blood cells, including the neutrophils, which is the first line of defense in the body against infection. If they go down, patients are at an increased risk of infections. Certain medications in this family can also place patients at an increased risk of diarrhea. Diarrhea, in turn, can cause electrolyte imbalances, dehydration, etc.
Liver and kidney function tests need to be monitored when patients are taking these agents. Some patients can have mild nausea and vomiting, but in general, these medications are fairly well tolerated.
3) How long do patients typically stay on CDK 4/6 inhibitors and how is treatment duration decided?
When we look at the different clinical trials that resulted in these medications being approved and available for our patients, on average, patients tend to stay on these inhibitors for about two years or so. However, it’s a bell-shaped curve, so two years is sort of representing the middle of that bell-shaped curve.
We unfortunately have some patients that stay on less than that time. Actively, we’re doing studies to determine how we can find which patients may have a lesser response than others. On the opposite side of the curve, we have some patients who have stayed on well past two years. In my clinic, I have several patients who have been on for three, four, five years, and counting. On average it’s about two years, but there are differences in responses given in each patient that determine the duration of response.
As far as how we determine how long patients stay on it, we usually monitor their response to treatment. We continue these inhibitors until the patient’s cancer responds to them or they have significant side effects that become a quality-of-life issue. Then, we have to take them off these medications.
4) What factors might influence whether a patient is a good candidate for CDK 4/6 inhibitors?
In general, CDK 4/6 inhibitors in combination with endocrine therapy or hormone-blocking therapy have been established as the frontline treatment option for these patients. We usually don’t have clinical parameters or other things that we use to test before we give patients this medication. If I have a patient who walks into my clinic and has just been diagnosed with Stage IV, hormone receptor-positive, HER2-negative breast cancer, that’s the first treatment I would deploy.
Watch the full interview with Dr. Advani here.
