A study of palbociclib and fulvestrant for advanced breast cancer that has continued to grow despite hormone treatment (PYTHIA)

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

Cancer type:

Breast cancer




Phase 2
This study is looking at adding palbociclib to a hormone treatment called fulvestrant for advanced breast cancer. 
It is for post menopausal Open a glossary item women whose:
  • breast cancer has spread to another part of the body (secondary breast cancer) or has come back after treatment in the same place (locally recurred)
  • breast cancer cells are oestrogen receptor positive (ER positive Open a glossary item)
  • breast cancer cells have low or no amounts of a protein called HER2 (HER2 negative cancer Open a glossary item)

More about this trial

Most breast cancers in women who have been through the menopause Open a glossary item need the hormone oestrogen to grow. Doctors call this oestrogen receptor positive breast cancer. Doctors treat this type of breast cancer with drugs that either reduce the amount of oestrogen the body makes or stops oestrogen getting to the cancer. This is called hormone treatment. 
Surgery followed by hormone therapy is one of the usual treatments for these women. But sometimes hormone therapies can stop working and the cancer can start to grow again. This means the cancer has become resistant Open a glossary item.
Researchers are looking for new treatments to help when breast cancer has become resistant to hormone therapy. In this study, they are looking at a drug called palbociclib.
Palbociclib is a type of targeted cancer drug. It is a type of cancer growth blocker. It stops signals that cancer cells use to divide and grow.
Based on previous research, researchers think that having palbociclib with a usual hormone therapy called fulvestrant will help to control the cancer for longer. 
The main aims of the study are to:
  • look for substances called biomarkers Open a glossary item to predict who will benefit most from treatment 
  • find out if palbociclib and fulvestrant is a useful combination of treatment
  • learn more about the side effects
  • find out 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. 
Please note: there is another study called AURORA running alongside this study. We have a summary of AURORA on our clinical trials database. It is collecting blood and tissue samples from people with breast cancer. To take part in this study you must first agree to take part in AURORA. 
Who can take part
You may be able to join this study if all of the following apply. 
  • have breast cancer that has spread elsewhere in the body or has come back and can’t be treated with the aim to cure 
  • have agreed to take part in the AURORA trial 
  • are female
  • have been through the menopause 
  • have had hormone therapy but it stopped working 
  • have cancer that has a large number of oestrogen hormone receptors (it is ER positive Open a glossary item)
  • have cancer that has few, or no receptors for HER2 Open a glossary item (it is HER2 negative)
  • have cancer that your doctor can see on a scan 
  • are well enough to carry out all your normal activities, apart from heavy physical work (performance status 0 or 1)
  • have agreed to take part in another study called AURORA – it is running alongside this study and is collecting blood and tissue samples (biopsies Open a glossary item) for research 
  • have satisfactory blood test results
  • can swallow tablets  
  • are at least 18 years old
Who can’t take part
You cannot join this study if any of these apply. 
Cancer related
  • have cancer that has spread to the brain, spinal cord or tissues surrounding the brain and is causing symptoms unless you have had treatment and you haven’t taken drugs to control fits or steroids Open a glossary item in the 4 weeks before joining the study
  • have had fulvestrant in the past 
  • have had palbociclib or a similar drug in the past
  • had more than 1 course of chemotherapy Open a glossary itemfor secondary breast cancer or breast cancer that has come back
  • have had any other cancer in the last 5 years apart from carcinoma insitu Open a glossary item of the cervix, basal cell skin cancer Open a glossary item or squamous cell skin cancer Open a glossary item that has been successfully treated
  • have had treatment with an experimental drug in the 4 weeks before joining the study
  • have moderate to severe side effects from previous cancer treatments apart from hair loss
Medical conditions
  • have had problems with your heart in the last 6 months such as a heart attack, angina that is not well controlled, an abnormal rhythm of your heart or congestive heart failure, 
  • have had a stroke, a mini stroke (TIA) or blood clot in your lung that is causing symptoms in the last 6 months 
  • have extra risk factors for a heart condition called torsade de pointes such as a family history of an abnormal heart rhythm called long QT syndrome
  • have low levels of certain minerals in your body such as calcium, potassium or magnesium 
  • have diabetes that isn’t well controlled with medication
  • have a problem with how your blood clots or are taking certain medication to thin your blood that means you can’t have fulvestrant injections
  • have HIV
  • have dementia, any other medical condition or mental health problem that the study team think would affect you taking part
You take drugs that affect enzymes called CYP3A.

Trial design

This is a phase 2 study. It is taking place in Europe and the UK. The researchers need 120 women to take part including 25 in the UK.
Everyone has fulvestrant and palbociclib.
Palbociclib is a capsule. You have treatment over 4 weeks. You take palbociclib everyday for 21 days then you have a week off.  Each 4 week period is a cycle of treatment. The doctor or research nurse will give you a fresh supply of tablets each month. 
You fill in a diary to note down when you take the capsules and include any side effects you might have. 
You have fulvestrant as 2 injections – 1 into each buttock.
The first day of each treatment cycle is called day 1. In the first month of treatment, you have fulvestrant on:
  • day 1
  • day 15
Then you have it once a month every month.
You have treatment for as long as it is helping and the side effects aren’t too bad. You stop treatment if your cancer gets worse. Your doctor will then talk to you about other treatment options.
Blood samples for research
The researchers will ask you to give some extra blood samples. You have these at the same time as your routine blood samples if possible. They plan to use the samples to look for biomarkers Open a glossary item to predict who will benefit from treatment.

Hospital visits

You see a doctor and have some tests before you can take part in this study. These include:
  • a physical examination
  • a heart trace (ECG Open a glossary item)
  • blood tests
  • CT scan or MRI scan
You might also need to have a bone scan or PET-CT scan.
You see the doctor for a check up and blood tests:
  • every 2 weeks in the first month
  • and then once a month after that
You have a CT scan or MRI scan every 3 months until your cancer gets worse. 
Follow up
When you finish treatment, you go to hospital every 3 months for up to a year for a check up. 

Side effects

As palbociclib is a new drug, there might be some side effects the study team don’t know about yet. They 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:
The most common side effects of fulvestrant include:
  • a reaction around the injection site such as pain or redness and swelling
  • changes to blood tests that monitor how your liver is working
  • feeling sick
  • weakness and tiredness
We have more information about fulvestrant.

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 Gianfilippo Bertelli

Supported by

ICR Clinical Trials and Statistics Unit (ICR-CTSU)
International Breast Cancer Study Group (IBCSG)

If you have questions about the trial please contact our cancer information nurses

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.

Last reviewed:

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