Alpelisib for PIK3CA-mutated breast cancer

Alpelisib is a targeted tablet for hormone receptor positive, HER2-negative metastatic breast cancer that carries a change, or mutation, in the PIK3CA gene. Around a third to four in ten of these cancers have such a mutation. PIK3CA makes part of a growth signalling pathway called PI3K. When it is mutated, the pathway stays switched on and helps the cancer grow and resist hormone therapy. Alpelisib blocks this signal. It is taken with fulvestrant, a hormone injection, usually after the cancer has grown on earlier hormone treatment, and studies showed the combination controlled the cancer for longer than fulvestrant alone in people with a PIK3CA mutation.

Why a mutation test is needed

Alpelisib only helps cancers with a PIK3CA mutation. A test on tumour tissue or a blood sample, sometimes called a liquid biopsy, is done before treatment is considered.

The main side effect to plan for

Alpelisib commonly raises blood sugar, because the same pathway helps the body handle glucose. Blood sugar is checked before and regularly during treatment, and many people need diabetes medicines while taking it.

Who may not be suitable

People with poorly controlled diabetes, a history of severe skin reactions, or those whose cancer has no PIK3CA mutation. Your oncologist checks your health carefully before starting.

For people with a PIK3CA-mutated cancer, alpelisib with fulvestrant can keep the cancer controlled for longer than fulvestrant alone. It does not make metastatic cancer go away for good, and side effects cause some people to reduce the dose or stop.

Blood sugar is manageable, but needs commitment

Frequent glucose checks, diet changes and medicines are often needed. People with pre-existing diabetes may need closer involvement of a diabetes specialist.

Rash can be prevented

Starting antihistamines before or with alpelisib lowers the chance of rash noticeably. Stopping early for a rash is often avoidable when it is caught early.

Newer options exist

Other drugs targeting the same pathway, and newer combinations, are being used or studied. Your oncologist can explain whether they are relevant to you.

What this page cannot tell you

It cannot tell you whether you have a PIK3CA mutation or would benefit. Ask your oncologist about testing.

Rash usually appears in the first few weeks. Most rashes are mild, but early action prevents them from becoming severe.

Preventive antihistamines

Taking a non-drowsy antihistamine from the start, as advised, reduces the chance of rash.

Skin care

Use gentle, fragrance-free soaps and moisturisers, and avoid hot showers and harsh sun.

When to call

Report any new rash promptly. Seek urgent help for blistering, peeling skin, mouth sores with fever, or swelling of the face.

Hormone-sensitive metastatic breast cancer is usually treated with a series of options over time. Alpelisib has a particular place in that sequence.

After first-line treatment

Most women start with a CDK4/6 inhibitor and hormone therapy. When the cancer grows on that combination, test results help choose what comes next. If a PIK3CA mutation is present, alpelisib with fulvestrant is one of the options considered.

Alongside other choices

Depending on other test results and how the cancer is behaving, your oncologist may also consider an oral SERD for an ESR1 mutation, a PARP inhibitor for a BRCA mutation, everolimus with exemestane, antibody-drug conjugates or chemotherapy.

Your own priorities

Daily tablets, frequent blood sugar checks and the chance of rash are part of the trade-off. Telling your oncologist what matters most to you, whether that is avoiding hospital visits, keeping side effects low or aiming for the longest control, helps shape a choice you can live with.

When faster control is needed

If the cancer is growing quickly or affecting organs significantly, chemotherapy may be preferred first because it tends to act faster.