How much does exemestane actually help? The numbers explained

Exemestane is an aromatase inhibitor tablet for hormone receptor positive breast cancer in women who have been through menopause, or in younger women whose ovaries have been switched off. After surgery for early breast cancer, its job is to lower the chance that the cancer comes back, either in the breast area or elsewhere in the body. It does this by stopping most of the oestrogen the body still makes after menopause. Large studies have shown that hormone therapy after surgery is one of the most effective parts of treatment for this type of cancer, and that aromatase inhibitors such as exemestane lower the risk of recurrence further than tamoxifen in postmenopausal women. Combined results from many trials found that, during the years when the two treatments differed, the chance of recurrence was roughly a fifth to a third lower with an aromatase inhibitor, and deaths from breast cancer were modestly lower over the long term. Exemestane has also been shown to help when women switch to it after a few years of tamoxifen. How much this means for you depends on your own starting risk. The same relative reduction gives a large benefit to someone whose cancer had a high chance of returning, and a smaller benefit to someone whose risk was already low. Taking the tablets regularly for the full planned time is what turns these trial results into real protection.

The benefit is real and well studied

Exemestane has been tested in large trials involving many thousands of women over many years.

Your own benefit depends on your risk

Tumour size, grade, lymph nodes and other features decide how much a risk reduction is worth to you.

Taking it steadily matters

Missing many doses or stopping early reduces the protection the trials showed.

Trial figures describe what happened to large groups of women. They cannot say exactly what will happen to one person.

Some cancers return despite treatment

Exemestane lowers the risk of recurrence, but it does not remove it. Some women do everything recommended and still have a recurrence.

Many would have stayed well anyway

Many women whose cancer never returns would have stayed well without hormone therapy. It is not possible to know in advance who those women are.

Older trials, newer patients

Treatment has improved since many of these trials began, so today's absolute benefits may differ.

What this page cannot tell you

It cannot calculate your personal benefit. Your oncologist can use your tumour details, and sometimes online risk tools, to estimate it with you.

The protection seen in trials depends on taking exemestane regularly for the planned time.

Build a daily habit

Take the tablet after the same meal each day, and use a pill box or phone reminder.

Treat side effects early

Joint pain, hot flushes and low mood are the common reasons women stop. Most can be eased, and switching to another aromatase inhibitor is sometimes possible.

Talk before stopping

If you are thinking of stopping, speak to your oncologist first. There may be a way to keep some or all of the benefit.