CDK4/6 Inhibitors

If you've been told you may need a CDK4/6 inhibitor, you'll probably have a lot of questions about what that involves. In this video, I'll explain what these medicines are, how we decide whether they're suitable for you and what to expect while you're taking one. CDK4/6 inhibitors are a targeted treatment for breast cancers whose growth is driven by hormones. To keep dividing, these cancer cells rely on two proteins called CDK4 and CDK6, and the medicine works by blocking them. That can slow or stop the cancer’s growth, and it’s why the treatment takes its name from those two proteins. Three of these medicines are used in UK breast cancer care, called palbociclib; ribociclib; and abemaciclib. Because they work differently from hormone treatment; they’re almost always given alongside it, so the two act on the cancer at the same time. Whether they're suitable for you starts with tests on tissue taken at your biopsy or surgery. A specialist in the laboratory checks whether the cancer cells carry receptors for oestrogen and progesterone. If they do, the cancer is described as hormone receptor positive; meaning hormones help to drive its growth. The same tissue is tested for a protein called HER2, and a second test is sometimes needed to confirm a borderline result. CDK4/6 medicines are used when the cancer is HER2 negative, while a different group of treatments is used when it's positive. Your oncologist or I will explain your own results and what they mean. If the tests show they're suitable, which of the three you're offered depends on your situation. Palbociclib is used only once the cancer has spread beyond the breast; while abemaciclib can sometimes be given on its own later in treatment. For women who haven't reached the menopause; ribociclib is given with treatment that switches off the ovaries. When they’re used also depends on the stage of the cancer. In early breast cancer; one may be added to hormone treatment after surgery for a set period, to lower the chance of it coming back. This is usually considered when that chance is higher than average, often because lymph nodes were involved. In advanced breast cancer, meaning cancer that has spread beyond the breast, these medicines are a standard option alongside hormone treatment. Trials have shown that adding one can lengthen the time before the cancer grows again, and your oncologist will explain what that may mean for you. Like any treatment, these medicines can cause side effects, and the most common is a drop in white blood cells, which raises your risk of infection. It's usually managed by adjusting the dose rather than stopping, and a lower dose doesn't mean the medicine is working less well. Tiredness, nausea and appetite changes are also common. Each medicine also has its own pattern of side effects. Palbociclib tends to lower blood counts more, and ribociclib can affect the heart's rhythm and the liver. Abemaciclib often causes diarrhoea early on and has been linked to blood clots, and all three can occasionally cause inflammation in the lungs. Because of these effects, you'll have frequent blood tests at first, and then usually once a month, to check your blood counts and liver. If you're taking ribociclib, you'll also have a heart tracing, called an ECG, before you start and at intervals afterwards. Between visits, keep your team's contact numbers, including the out-of-hours number, somewhere you can find them easily. Please also tell us about any other medicines you take. Contact your team urgently if your temperature goes above 37.5 degrees or you feel shivery, or if you develop new breathlessness or chest pain. The same applies to severe diarrhoea; unusual bruising or bleeding; or a painful, swollen leg. It's important to remember that treatment decisions are always personal and made together with you and your team. If you'd like to talk through what this might mean for you, please get in touch.