A trial looking at palbociclib and letrozole before breast cancer surgery (PALLET)

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 trial is looking at palbociclib and letrozole to treat women before they have surgery to remove their breast cancer. It is recruiting women who have been through the menopause Open a glossary item and have breast cancer that is sensitive to the female hormone oestrogen (oestrogen receptor positive or ER positive Open a glossary item).

This trial is supported by Cancer Research UK.

More about this trial

Doctors sometimes treat breast cancer with hormone therapy before surgery. This is called neo adjuvant therapy. It can help to shrink the cancer before surgery so that the operation is easier and the surgeon may not need to remove as much breast tissue.

In this situation, doctors often give a hormone therapy called letrozole. They think that another drug called palbociclib may be useful alongside letrozole. Palbociclib is a type of biological therapy. It targets and blocks the proteins that help cancer cells to divide and grow.
The aim of the trial is to find out if palbociclib and letrozole is better than letrozole alone as treatment before surgery for breast cancer.

Who can enter

You may be able to join this trial if all of the following apply:

  • you are female, have early stage breast cancer and you are postmenopausal Open a glossary item
  • your doctor thinks that you are suitable for neoadjuvant therapy Open a glossary item
  • your breast cancer is sensitive to the female hormone oestrogen (oestrogen receptor positive or ER positive Open a glossary item) and does not have receptors for a protein called HER2 Open a glossary item (HER2 negative)
  • your cancer measures at least 2 cm in any direction (when measured by ultrasound)
  • you are well enough to carry out all your normal activities, apart from heavy physical work (performance status of 0 or 1)
  • you have satisfactory blood test results
  • you must be able to swallow tablets

You cannot join this trial if any of these apply. You:

  • have inflammatory breast cancer or breast cancer which cannot be removed with surgery
  • have breast cancer in both breasts
  • have already had treatment for your breast cancer (including hormone therapy, chemotherapy or biological therapy)
  • have already had radiotherapy for your breast cancer
  • have taken hormone replacement therapy or any other medicine containing oestrogen (including vaginal oestrogens) in the 4 weeks before joining the trial
  • have had breast cancer in the past
  • have had any other cancer in the last 5 years apart from carcinoma in situ of the cervix or non melanoma skin cancer
  • have certain heart problems (your doctor can advise you about this)
  • take other medication that affects body substances called CYP enzymes (your doctor can advise you about this)
  • are hepatitis B or hepatitis C positive
  • are HIV positive and you are having antiviral treatment
  • have any other serious medical condition or mental health problem that your doctor thinks could affect you taking part

Trial design

This is an international phase 2 trial. The researchers need 306 women to join.

It is a randomised trial. The people taking part are put into 4 different treatment groups by a computer. Neither you nor your doctor will be able to decide which group you are in:

  • people in group A have letrozole for 14 weeks
  • people in group B have letrozole for 2 weeks followed by letrozole and palbociclib for the next 12 weeks
  • people in group C have palbociclib for 2 weeks followed by letrozole and palbociclib for the next 12 weeks
  • people in group D have letrozole and palbociclib for 14 weeks

For every 3 people in group A, there are 2 people in group B, 2 in group C and 2 in group D.

You have letrozole as a tablet and palbociclib as a capsule. A doctor or nurse in the trial team will explain when and how often you take your drug or drugs.

Whichever group you are in, after the 14 weeks, you have standard treatment with letrozole until you have surgery.

As part of this trial, the researchers will take samples (biopsies) of cancer tissue from your breast. You have these before you start treatment, 2 weeks after the start of treatment and then again when you finish the trial treatment.

The researchers will look at the genetic information in these samples (as well as from blood samples) and record how well the treatment works for each person. They hope to find substances called biomarkers Open a glossary item that may help doctors to work out how well these treatments will work for individual women.

Hospital visits

You will see the doctors and have some tests before you start treatment. The tests include:

  • physical examination
  • heart trace (ECG Open a glossary item)
  • blood tests​
  • ultrasound scan of your breast

During the trial you go to hospital every week for the first month, then every other week for the remaining 10 weeks. At each appointment you see a doctor who will ask you about any side effects. You also have blood tests. You have physical examinations at every other visit.

You have another heart trace after 6 weeks and again at 14 weeks, and an ultrasound scan when you stop treatment in this trial.

The trial team would like to see you again about 30 days after you finish the trial treatment and again about a year after you first joined the trial. The doctor will examine you and ask how you are and if you have any symptoms. You also have a blood test.

Side effects

The most common side effects of letrozole include:

We have more information about letrozole.

The most common side effects of palbociclib are

While taking palbociclib you should not eat grapefruit or drink grapefuit juice, or take St John's Wort. This is because it can interfere with the way palbociclib works. Before you start taking any new medicine (including those sold over the counter) you should discuss this with your research nurse or doctor first.

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

Professor Stephen Johnson

Supported by

Cancer Research UK
Experimental Cancer Medicine Centre (ECMC)
Institute of Cancer Research (ICR)
The Royal Marsden NHS Foundation Trust

Questions about cancer? Contact our 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.

Harriet wanted to try new treatments

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“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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