PIK3CA is a gene that can contribute to the growth of breast, ovarian, colon, or brain cancer when mutated. A doctor can test you for this genetic mutation.

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  • A mutation in the PIK3CA gene can cause cells to divide and replicate uncontrollably. It contributes to the growth of many cancers, including metastatic breast cancer (MBC).
  • If your tumor has a PIK3CA mutation, new treatments that specifically target this mutation could be used to treat your cancer.
  • The Food and Drug Administration (FDA) has approved a treatment called alpelisib (Piqray) specifically for people with HR-positive and HER2-negative MBC whose tumors have a PIK3CA mutation.

If you’ve received a diagnosis of breast cancer and your cancer returns or doesn’t improve after initial treatment, your doctor will likely perform additional tests to help understand if and where the cancer has spread.

Tests can also identify specific genes, proteins, and other molecular factors unique to your tumor. Your doctor can use these test results to inform treatment decisions.

Genetic tests look for mutations in genes. Genes are segments of DNA inside your cells that give your body instructions for how to work. A mutation is an error in the gene.

One type of gene mutation that’s known to affect people with breast cancer is called PIK3CA.

The PIK3CA gene holds the instructions for making a protein called p110 alpha (p110α). P110α has many functions in the body, including:

  • cell growth and division
  • cell movement
  • producing proteins
  • transport of materials in cells
  • cell survival

PI3K signaling may also be involved in the regulation of some hormones.

A mutation in the PIK3CA gene can disrupt this process, causing cells to divide and replicate uncontrollably. This contributes to the growth of many cancers, including:

  • breast cancer
  • ovarian cancer
  • colon cancer
  • brain cancer

PIK3CA mutations are found in up to 40 percent of estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancers.

If your tumor is found to have a PIK3CA mutation, new treatments that specifically target the mutation in the PIK3CA gene could be helpful.

Metastatic breast cancer (MBC), also known as stage 4 or advanced breast cancer, means that the cancer has traveled from the breast tissue, or metastasized, to other parts of the body, like the liver, lungs, or brain.

Survival rates are lower in advanced breast cancer, but the right treatment can improve both length and quality of life.

According to a 2018 study involving more than 10,000 people, genetic mutations like those found in PIK3CA aren’t as common in early stage breast cancers.

But when PIK3CA mutations do occur in these cases, their presence is often associated with better clinical outcomes.

However, testing for a PIK3CA mutation isn’t typically done in people with early stage breast cancer. Clinical guidelines recommend testing for PIK3CA mutations after a person has metastases from breast cancer.

Knowing your tumor type and mutation status can help your doctor decide which treatment or combination of treatments are likely to work best to treat your cancer.

A 2020 study in 649 people found that people with HR-positive, HER2-negative breast cancers and PIK3CA mutations are less sensitive, or resistant, to chemotherapy drugs, including paclitaxel, doxorubicin, and 5-fluorouracil.

This means that chemotherapy is less likely to help treat the cancer.

In 2019, the Food and Drug Administration (FDA) approved a treatment specifically for people with MBC whose tumors have a PIK3CA mutation. This drug, known as alpelisib (Piqray), is considered a “PI3K inhibitor.”

Piqray can be used in postmenopausal women and men with advanced breast cancer whose tumors have the PIK3CA mutation and are HR-positive and HER2-negative.

Piqray should be used in combination with a hormone treatment known as fulvestrant (Faslodex). Piqray is a tablet taken by mouth.

An FDA-approved companion diagnostic test, called therascreen PIK3CA RGQ PCR Kit, is first used to find out whether you have the PIK3CA mutation.

For this test, a healthcare professional will either take a blood sample or a small amount of cancer tissue from your tumor and send it to a lab.

If the test results show the presence of a mutation in the PIK3CA gene in the cancer tissue, you will be eligible for treatment with alpelisib (Piqray).

Alpelisib’s approval was based on the results of a clinical trial called the SOLAR-1 study.

The trial included 572 female and male participants with HR-positive and HER2-negative breast cancer who already tried treatment with an aromatase inhibitor, like anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin).

The study found that alpelisib significantly improved the amount of time people lived without their breast cancer getting worse. This is called progression-free survival.

The median progression-free survival was 11 months for people who received alpelisib plus fulvestrant. It was 5.7 months for people who received a placebo plus fulvestrant. This effect was stronger in people with a mutation in the PIK3CA gene.

Additional clinical trials are underway to assess new combinations of treatments involving alpelisib. These trials will also look at the role of similar gene mutations (for example, PIK3CA amplifications or PIK3R1 mutations) to better select people for this therapy.

There are also several other PIK3CA inhibitors under investigation in clinical trials in people with advanced breast cancer and a mutation in the PIK3CA gene, including taselisib and pictilisib.

Research suggests that recurrence-free survival may be better for people who have a PIK3CA mutation in their tumors compared with people who don’t have the mutation.

However, MBC is still difficult to treat. Many individual factors play a role in survival rates, including how well certain treatments work for your cancer type.

The approval of alpelisib (Piqray) means there’s now a targeted treatment for people with advanced breast cancer who have a PIK3CA mutation.

People who take alpelisib may live longer without their cancer progressing compared with people who have a PIK3CA mutation and don’t take this drug.

However, not all people with PIK3CA mutations experience the same benefits from treatment with a PI3K inhibitor like alpelisib.

More research is needed to determine the best treatments for people who don’t benefit from this type of treatment.

If you have MBC, knowing your PIK3CA gene status can be helpful if your cancer hasn’t improved or has come back after treatment, especially if you have HR-positive/HER2-negative breast cancer.

Ask your doctor if you should get tested for the mutation. If your test results are positive for a mutation in PIK3CA, newer treatments that specifically target it could help improve your outlook.