A study of palbociclib with hormone therapy for women with early breast cancer (PENELOPE-B)

Please note - this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Breast cancer




Phase 3

This study is for women who have had chemotherapy before surgery. It is open to women whose breast cancer cells:

  • have receptors for the hormones oestrogen or progesterone (is hormone receptor positive)
  • are HER2 negative Open a glossary item

Doctors call this luminal type breast cancer. 

More about this trial

Surgery and chemotherapy are the usual treatments for early breast cancer. But sometimes, there are some remaining cancer cells after treatment. This means you have an increased risk of the cancer coming back. So you usually have 5 years of hormone therapy such as tamoxifen, letrozole, anastrozole or exemastane.

Researchers are looking at new treatments to improve hormone therapy.

In this study, they looking at a drug called palbociclib. It is a targeted cancer drug.

It targets and blocks the proteins that help cancer cells to divide and grow. Doctors think having it alongside hormone therapy might help stop the cancer coming back. But they don’t know for sure, so they want to find out more.

In this study, some women have hormone therapy and palbociclib. And some women have hormone therapy and a dummy drug (placebo Open a glossary item)

The aims of this study are to find out:

  • if palbociclib and hormone therapy can increase the time before the cancer comes back
  • if having palbociclib and hormone therapy can help women live longer
  • what the side effects are
  • about quality of life Open a glossary item

Who can enter

The following bullet points list the entry conditions for this study. Talk to your doctor or the study team if you are unsure about any of these. They will be able to advise you.

You might be able to join this study if all of the following apply.

  • You are a woman with invasive breast cancer
  • You have had at least 16 weeks of chemotherapy before surgery including 6 weeks of a taxane drug Open a glossary item - you might be able to take part if your cancer got worse before you completed the 16 weeks of chemotherapy but you had the 6 weeks of taxane treatment
  • You have had surgery to remove the cancer in your breast
  • There are some remaining cancer cells in your breast or lymph nodes Open a glossary item following your chemotherapy and surgery
  • You have had radiotherapy after surgery
  • You have had surgery within 16 weeks of joining the study or radiotherapy within 10 weeks
  • There is a tissue sample of your cancer available for the study team to do some tests
  • Your cancer is hormone receptor positive and HER2 negative
  • You are well enough to carry out all your normal activities, apart from heavy physical work (performance status 0 or 1)
  • You are willing to use reliable contraception during treatment and for up to 90 days afterwards if there is any chance that you could become pregnant
  • You have satisfactory blood test results
  • You are at least 18 years old

You cannot join this study if any of these apply. You

Cancer related

  • Have breast cancer that grew into surrounding tissue or spread to another part of the body when you were having chemotherapy before surgery – you might be able to take part if the cancer got worse in the area it started
  • Have had treatment with palbociclib or a similar drug in the past
  • Have side effects from chemotherapy unless they are mild apart from hair loss
  • Have had any other cancer in the last 5 years apart from carcinoma insitu of the cervix (CIS) or basal cell skin cancer Open a glossary item that was successfully treated
  • Are having or have had treatment with an experimental drug as part of a clinical trial in the last 30 days

Medical conditions

  • Have problems with your heart, such as a heart attack in the last 6 months, high blood pressure that is not well controlled, angina that is not well controlled, an abnormal rhythm of your heart, congestive heart  failure, or heart bypass surgery
  • Have had a stroke or blood clot in your lungs in the last 6 months
  • Have a digestive system Open a glossary item problem such as inflammatory bowel disease, long term diarrhoea, short bowel syndrome or any surgery to your stomach or gut (intestines)
  • Have a problem with the way your liver and kidneys work, for example your kidneys aren’t filtering urine properly
  • Have had major surgery in the last 2 weeks
  • Have an infection that isn’t getting better or a wound that isn’t healing
  • Have HIV
  • Have hepatitis B or hepatitis C
  • Have any other serious medical condition or mental health problem that the study team think could affect you taking part


  • Are sensitive to palbociclib, similar drugs or anything they contain
  • Have taken medication that affects body substances called CYP enzymes in the last 7 days
  • Are pregnant or breastfeeding

Trial design

This phase 3 study is taking place worldwide. The researchers need 1,250 people to take part including 35 in the UK.

It is a randomised study. You are put into 1 of 2 groups. You have one of the following:

  • hormone therapy and palbociclib
  • hormone therapy and a dummy drug (placebo)

Neither you nor your doctor will be able to decide which group you are in. And neither of you will know which group you are in. This is called a double blind study. 


Palbociclib and the dummy drug are capsules. You have treatment over 4 weeks. You take palbociclib or the dummy capsules everyday for 21 days then you have a week off.  Each 4 week period is a cycle of treatment.

You have treatment for up to a year as long as it is helping and the side effects aren’t too bad.

You have hormone therapy for 5 years. The study team will tell you more about the type of hormone therapy you have and how often you take it.

Quality of life
Everybody taking part will be asked to fill out a questionnaire before starting treatment, at set times during the study and after finishing treatment. The questionnaire will ask about any side effects you have had and about how you have been feeling. This is called a quality of life study.

Samples for research
The doctors will ask to take some extra blood samples. Where possible, you have these at the same time as your routine blood tests.

They plan to look at:

  • what happens to palbociclib in the body (pharmacokinetics Open a glossary item)
  • substances called biomarkers Open a glossary item to help work out why treatment might work for some people and not for others
  • whether there is DNA from cancer cells known as circulating tumour DNA or ctDNA in your blood

You don’t have to agree to give a blood sample looking at circulating tumour DNA. You can still take part in the study.

Hospital visits

You see a doctor and have some tests before you can take part. These include:

You might also have a bone scan Open a glossary item and PET-CT scan.

You see the doctors for a check up and some blood tests every:

  • 2 weeks for 2 months
  • once a month after that

The blood tests check your general health and you will also have a blood test regularly that checks your glucose (sugar) levels.

When you finish treatment, the study team will follow you up for 3 years. You have a:

  • routine check up every 6 months
  • mammogram or MRI once a year

Side effects

As palbociclib is a new drug, there might be some side effects we don’t know about yet. The study team will monitor you during the time you have treatment and you’ll have a phone number to call them if you are worried about anything.

So far the most common side effects include:

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Dr Andreas Makris

Supported by

German Breast Group (GBG)
ICR Clinical Trials and Statistics Unit (ICR-CTSU)

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Harriet wanted to try new treatments

A picture of Harriet

“I was keen to go on a clinical trial. I wanted to try new cancer treatments and hopefully help future generations.”

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