Several tests can help your doctor diagnose metastatic breast cancer, predict how it will act, and find the most effective treatment for you. Genetic tests look for mutations to genes, the segments of DNA inside your cells that control how your body works.
One of the genetic mutations your doctor may test for is PIK3CA. Read on to learn how having this gene mutation might affect your treatment and outlook.
The PIK3CA gene holds the instructions for making a protein called p110α. This protein is important for many cell functions, including telling your cells when to grow and divide.
Certain people may have mutations in this gene. PIK3CA gene mutations cause cells to grow uncontrollably, which can lead to cancer.
PIK3CA gene mutations are linked to breast cancer, as well as to cancers of the ovary, lung, stomach, and brain. Breast cancer likely stems from a combination of changes to PIK3CA and other genes.
PIK3CA mutations affect about
ER-positive means your breast cancer grows in response to the hormone estrogen. HER2-negative means you don’t have abnormal HER2 proteins on the surface of your breast cancer cells.
If you have an ER-positive, HER2-negative breast cancer, the doctor who treats your cancer may test you for the PIK3CA gene mutation. In 2019, the FDA approved a test called therascreen to detect mutations in the PIK3CA gene.
This test uses a sample of your blood or tissue from your breast. The blood test is done like any other blood test. A nurse or technician will draw blood from your arm with a needle.
The blood sample then goes to a lab for analysis. Breast cancers shed small pieces of their DNA into the blood. The lab will test for the PIK3CA gene in your blood sample.
If you get a negative result on the blood test, you should have a biopsy to confirm it. Your doctor will remove a sample of tissue from your breast during a minor surgical procedure. The tissue sample then goes to a lab, where technicians test it for the PIK3CA gene mutation.
Having the PIK3CA mutation may prevent your cancer from responding as well to hormone therapy used to treat metastatic breast cancer. It also means you’re a candidate for a new drug called alpelisib (Piqray).
Piqray is a PI3K inhibitor. It’s the very first drug of its kind. The FDA approved Piqray in May 2019 to treat postmenopausal women and men whose breast tumors have the PIK3CA mutation and are HR-positive and HER2-negative.
The approval was based on the results of the SOLAR-1 study. The trial included 572 women and men with HR-positive and HER2-negative breast cancer. The participants’ cancer continued to grow and spread after they’d been treated with an aromatase inhibitor like anastrozole (Arimidex) or letrozole (Femara).
Researchers found that taking Piqray improved the amount of time people lived without their breast cancer getting worse. For people who took the drug, their cancer didn’t progress for 11 months, compared to an average of 5.7 months in people who didn’t take Piqray.
Piqray is combined with the hormone therapy fulvestrant (Faslodex). Taking the two drugs together helps them work better.
If you have a PIK3CA mutation, you may not respond as well to drugs typically used to treat metastatic breast cancer. Yet the introduction of Piqray means that there’s now a drug that specifically targets your genetic mutation.
People who take Piqray plus Faslodex live longer without their disease progressing compared to those who don’t take this drug.
Knowing your PIK3CA gene status can be helpful if your cancer hasn’t improved or has come back after treatment. Ask your doctor if you should get tested for this gene. If you do test positive, a new treatment could help improve your outlook.