A CDK4/6 inhibitor for advanced breast cancer
Palbociclib
A targeted cancer medicine taken with hormone therapy to slow the growth of certain advanced breast cancers.
What is Palbociclib?
Palbociclib is a specialist cancer medicine used to treat certain types of advanced or secondary breast cancer that are driven by hormones (hormone-receptor positive) and are not HER2 positive. It is a CDK4/6 inhibitor, meaning it blocks proteins that cancer cells use to divide, and it is taken by mouth alongside hormone therapy. Its main effect is a drop in white blood cells (neutropenia), which raises the risk of infection, so regular blood tests are needed. Tiredness is common, and a serious but uncommon lung problem (inflammation called pneumonitis) can occur. It can harm a developing baby, so reliable contraception is important.
Education and reference only. This is a plain-language guide to Palbociclib — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Palbociclib is a targeted cancer medicine used to treat advanced or secondary breast cancer that is hormone-receptor positive and HER2 negative. It belongs to a group called CDK4/6 inhibitors, which work by interrupting the signals cancer cells use to grow and divide. It is taken by mouth as a capsule or tablet, in cycles, and is always used together with hormone therapy rather than on its own. It is prescribed and supervised by a cancer specialist team, who monitor it closely with blood tests.
How it works
Cancer cells grow by going through a repeated cycle of division, and proteins called CDK4 and CDK6 help push them through that cycle. Palbociclib blocks these proteins, which stalls the cycle and slows or stops the cancer cells from multiplying. Because the breast cancers it is used for are also fuelled by hormones, it is combined with hormone therapy so the two work together to control the cancer for longer. The same effect on dividing cells is why it can lower the number of white blood cells made in the bone marrow, which is why blood counts are checked regularly.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist cancer medicine used in the UK to treat certain types of advanced or secondary breast cancer, taken alongside hormone therapy.
Practical use
How to take Palbociclib
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth once a day in the cycles your cancer team sets out, usually with a break built in to let blood counts recover.
- Swallow it whole with water; follow your team's advice on whether to take it with food.
- Keep all your blood test appointments, as these check your white blood cells and guide your dose.
- Take your hormone therapy as prescribed too, since palbociclib is used alongside it, not instead of it.
- Use reliable contraception during treatment and for the time afterwards your team advises, as it can harm a developing baby.
Weighing it up
Advantages & disadvantages of Palbociclib
Advantages
- Can slow the growth of certain advanced breast cancers and help control them for longer when added to hormone therapy.
- Taken by mouth at home rather than as an infusion.
- A targeted treatment that works on the cancer's growth signals.
Disadvantages
- Commonly lowers white blood cells, raising the risk of infection and needing regular blood tests.
- Often causes tiredness, which can build up over time.
- Can rarely cause serious lung inflammation and can harm a developing baby.
Practical use
Good to know
The most important thing to understand is that palbociclib commonly lowers your white blood cells, especially a type called neutrophils, which fight infection; this is why you will have regular blood tests and why the dose may be paused or adjusted. Because of this, you should report signs of infection such as a fever, sore throat, chills or feeling generally unwell straight away, as an infection can become serious quickly when these cells are low. Tiredness is very common and can build up over time. A less common but serious problem is inflammation in the lungs (pneumonitis), so new or worsening breathlessness, cough or chest discomfort should be reported promptly. It is taken in cycles, often with breaks built in to let blood counts recover, and it is important to take it exactly as scheduled. It can harm a developing baby, so reliable contraception is needed during treatment and for a time afterwards.
Who should not take it / use with caution
- People who have had a serious allergic reaction to palbociclib should not take it.
- It is not used in pregnancy because it can harm a developing baby, and breastfeeding is avoided during treatment.
- It is used with caution in people with significant liver problems or a current serious infection, under specialist guidance.
Monitoring
- Regular blood tests to check white blood cells and other blood counts, which guide the dose.
- Watching for signs of infection and for new or worsening breathlessness or cough.
- Reviewing how well the cancer is responding alongside the hormone therapy.
Side effects
- A drop in white blood cells (neutropenia), which raises the risk of infection.
- Tiredness, mouth soreness, nausea or hair thinning.
- Less commonly, a drop in other blood cells, or signs of infection such as fever that need urgent attention.
- Rarely but seriously, inflammation in the lungs (pneumonitis) causing breathlessness or cough, which needs prompt medical attention.
Key interactions
- Some medicines and foods, such as grapefruit, can raise palbociclib levels, so tell your team about everything you take.
- Other medicines can lower its levels and make it less effective, so these are reviewed by your team.
- It may affect, or be affected by, certain other medicines processed by the liver, so a full medicines list is important.
Available as: Capsules or tablets taken by mouth.
Answers
Palbociclib: frequently asked questions
What is palbociclib used for?
It is used to treat certain advanced or secondary breast cancers that are hormone-receptor positive and HER2 negative, taken by mouth alongside hormone therapy.
Why do I need so many blood tests?
Palbociclib commonly lowers your white blood cells, which fight infection, so blood tests check these counts and help your team adjust the dose safely.
What should I do if I get a fever?
Report a fever or other signs of infection such as a sore throat or chills straight away, because infections can become serious when your white blood cells are low.
Why is it taken with hormone therapy?
The breast cancers it treats are fuelled by hormones, so palbociclib is combined with hormone therapy to control the cancer more effectively than either alone.
Is it safe in pregnancy?
No. Palbociclib can harm a developing baby, so reliable contraception is needed during treatment and for a time afterwards.
Authoritative sources
- BNF
- NICE CKS
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