How much does alpelisib actually help? The numbers explained

The main evidence for alpelisib comes from a large randomised study called SOLAR-1. It included people with hormone receptor positive, HER2-negative advanced breast cancer whose cancer had grown during or after hormone treatment. Everyone received fulvestrant, and half also received alpelisib. In those whose cancer carried a PIK3CA mutation, the typical time before the cancer grew was roughly eleven months with alpelisib, compared with under six months with fulvestrant alone, so the average gain was about five months of control. The cancer shrank in about a third of people with measurable disease on alpelisib, compared with about one in six on fulvestrant alone. Typical overall survival was about eight months longer with alpelisib, but this difference did not reach the statistical threshold the study had set, so it could have been due to chance. In people without a PIK3CA mutation, alpelisib did not show a meaningful benefit. Very few people in SOLAR-1 had received a CDK4/6 inhibitor first, which is now standard. A later study, BYLieve, looked at alpelisib after a CDK4/6 inhibitor and found that around half of people were alive without their cancer growing at six months, though that study had no comparison group. Benefit came with real side effects, and about a quarter of people in SOLAR-1 stopped alpelisib because of them. These figures are averages, and your own result may differ.

Longer control with a mutation

About five months more before growth on average.

Survival gain uncertain

Survival was longer, but the difference could have been due to chance.

No benefit without a mutation

That is why testing comes first.

Trial numbers are the best guide available, but they need careful interpretation.

The world has changed since the trial

Most people now receive a CDK4/6 inhibitor first, so benefit today may be smaller than SOLAR-1 showed.

Averages hide a wide range

Some people stayed controlled far longer, and others gained little.

Side effects affect real-world benefit

People who stop early because of side effects may not get the full benefit.

What this page cannot tell you

It cannot predict how alpelisib will work for you. Your oncologist can discuss your likely benefit.

Months of control can mean different things to different people.

Delaying chemotherapy

Longer control on tablets and hormone treatment can push back the need for chemotherapy.

Symptom relief

When cancer shrinks, pain or breathlessness caused by the cancer may ease.

The trade-off

Sugar checks, diet changes and side effects are part of the price. Some people feel it is worth it and others do not.

Your first scan is often the moment study numbers become personal. Knowing what different results mean can ease the wait.

Stable is a good result

Cancer that has not grown counts as benefit, even without shrinkage.

Shrinkage is encouraging

It suggests the cancer is responding, and treatment usually continues.

Growth means a new plan

If the cancer has grown, your oncologist will talk through the next options with you, without delay.