This site is intended for patients in Great Britain (England, Scotland and Wales) who have been prescribed PIQRAY®▼ (alpelisib) + fulvestrant.

It looks like you are using an older version of Internet Explorer which is not supported. We advise that you update your browser to the latest version of Microsoft Edge, or consider using other browsers such as Chrome, Firefox or Safari.

What is the PIK3CA mutation?

Your doctor will have tested you to see what subtype of advanced breast cancer (aBC) you have.

Why is this important?

Finding out your aBC subtype is the key to choosing the most suitable treatment for your condition.1 Your aBC subtype tells you whether or not your breast cancer cells use hormones or particular proteins to grow and it can also tell you which gene mutations have caused the breast cells to grow in the wrong way.1

Your doctor determined your subtype by testing for substances in your blood, urine or body tissue called biomarkers.1 Biomarker testing helps doctors choose the right treatment plan for your type of cancer.2–4

In breast cancer, some useful biomarkers include:2,5,6

  • Hormone receptors (HR)
  • Human epidermal growth factor receptor 2 (HER2)
  • PIK3CA mutations

What do hormone receptors do in aBC?

What do hormone receptors do in aBC image

Some breast cancer cells use hormones like oestrogen or progesterone to grow. These hormones can bind to cells that have receptors that fit them. It is helpful to know if your aBC cells have a lot of these receptors – known as HR-positive (HR+) aBC – when selecting the right treatment.1

What does HER2 do in aBC?

HER2 is a receptor on the outside of cancer cells that helps them grow and divide.7 When breast cancer cells have a lot of HER2-positive (HER2+) receptors, they may grow more quickly and be more likely to spread to other parts of the body.7

What do PIK3CA mutations do in aBC?

Each of your genes contains a set of instructions that tells a cell how to build a different part of itself.5,8 Some gene mutations (errors) cause cells to grow in unhealthy ways, as happens in cancer.1,9

The PIK3CA gene instructs part of the cell called phosphatidylinositol-3-kinase α (PI3Kα).5,8 When PIK3CA has a mutation, it gives the wrong instructions for PI3Kα causing PI3Kα to become ‘activated’.5,8

PIK3CA mutation infographic

Activated PI3Kα tells the cell to grow and divide more than normal, which can:5,8

  • Cause the tumour to grow
  • Make certain treatments less effective
  • Lead to a worse outcome for patients with aBC
40% of patients icon


Up to 40% of patients with HR+/HER2- aBC have a PIK3CA mutation.10,11

Why is this important to me?

Treatments are available to target PIK3CA mutations in patients with aBC.

PIQRAY®▼ (alpelisib) is a treatment given to postmenopausal women, or men, with locally advanced or metastatic breast cancer who:1

positive mutation icon

Have tested positive for a mutation in the PIK3CA gene

HR+ HER2- icon

Have HR+, HER2- aBC

hormone progression icon

Have had a progression of their aBC following hormone-based therapy

In these patients, PIQRAY® is prescribed together with another medication called fulvestrant.1

What should I know about testing for biomarkers like PIK3CA mutation?

Biomarker testing

Biomarker testing, using a blood or tissue sample, may be done when your doctor first discovers that your breast cancer has spread,2 or if it starts growing or spreading again after a treatment is given (also called progression).2,12

Biomarkers found

Biomarkers are found and measured by testing your blood or tissue, using biomarker analysis for biomarker identification.2

Which biomarkers

Finding out which biomarkers you have helps your doctor choose appropriate treatments.1,13

What biomarkers do:14

Guide treatment decisions Determine how well your treatment is working
Predict how your cancer may respond to treatment Signal that the cancer is returning
Glossary of terms banner image

Use the aBC glossary as a quick guide to any terms that are new to you


aBC, advanced breast cancer; PIK3CA, phosphatidylinositol-4,5-biphosphate 3-kinase catalytic subunit alpha.


  1. National Cancer Institute. Breast cancer treatment (PDQ®)–patient version. Available at: [Accessed January 2022].
  2. American Society of Clinical Oncology. Biomarkers to guide treatment for early-stage breast cancer. Available at: [Accessed January 2022].
  3. National Cancer Institute. Biomarker. NCI Dictionary of Cancer Terms. Available at: [Accessed January 2022].
  4. Karley D, et al. World J Oncol. 2011;2(4):151–157.
  5. US National Library of Medicine. PIK3CA gene. Genetics Home Reference. Available at: [Accessed January 2022].
  6. My Cancer Genome. PIK3CA. Available at: [Accessed January 2022].
  7. HER2 status. Available at: [Accessed January 2022].
  8. Sobhani N, et al. J Cell Biochem. 2018;119(6):4287–4292.
  9. American Cancer Society. Caregiver resource guide. Available at:[Accessed January 2022].
  10. Sabine VS, et al. J Clin Oncol. 2014;32(27):2951–2958.
  11. Andre F, et al. N Engl J Med. 2019;380(20):1929–1940.
  12. Blood marker tests. Diagnosing and Monitoring Breast Cancer Available at: [Accessed January 2022].
  13. National Cancer Institute. Tumor markers. Available at: [Accessed January 2022].
  14. Duffy MJ, et al. Eur J Cancer. 2017;75:P284–298.

▼This medicine is subject to additional monitoring. This will allow quick identification of new safety information. You can help by reporting any side effects you may get. See for how to report side effects.

UK | January 2022 | 147261