Anastrozole: the daily breast cancer pill tipped to save thousands of lives

Nearly 300,000 women in England will be offered a preventative pill to help them avoid breast cancer.

The drug, anastrozole, has been available for years as a breast cancer treatment, and had already been recommended for prevention by the UK's health cost regulator. But it has become the first drug to be licensed for a new use under the "pioneering" multi-agency Medicines Repurposing Programme set up in 2021, said NHS England. 

Breast cancer is the most common cancer in England, with about 50,000 people diagnosed each year. While survival rates have improved, it still claims about 11,500 lives each year. For post-menopausal, at-risk women, the off-patent drug can nearly halve the chance of developing the disease if taken every day for five years. 

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NHS chief executive Amanda Pritchard called the news "a new era for cancer prevention". The pills, which cost only 4p a day, would follow statins in having a "transformative", life-saving impact, she wrote for The Telegraph.

What is anastrozole and how does it work?

Anastrozole is a type of hormone treatment that lowers the level of oestrogen in the body. According to NHS England, the medication is an "aromatase inhibitor", which cuts down the amount of oestrogen a body makes by blocking the "aromatase" enzyme. 

Common side-effects mirror those of menopause, such as hot flushes and sweating, vaginal dryness or bleeding, tiredness and low mood. Patients usually take a small tablet every day for up to five years. 

Anastrozole has been used for many years to treat breast cancer, and its power to prevent the disease has been shown in key trials for years. It was first backed for use as a preventative option by the National Institute for Health and Care Excellence (Nice) in 2017, after scientists found that the protective effects lasted for years after women stopped taking the medication.

However, widespread prescribing was "stymied", said The Telegraph's health editor Laura Donnelly, because the drug was only licensed for treatment, not prevention, of breast cancer. The off-patent drug could only be prescribed "off-label" – "severely limiting take-up".

Why has it become available for prevention now? 

Anastrozole has been relicensed via a "repurposing" programme, which aims to get drugs licensed for one treatment approved for another if found to be effective. The programme, set up in 2021, is hosted by NHS England and supported by Nice, the Medicines and Healthcare products Regulatory Agency (MHRA) and other agencies. 

It "builds on work done during the pandemic", said Donnelly, when arthritis drugs and steroids were "repurposed" as Covid treatments. Under the programme, the MHRA "licensed the new purpose" for anastrozole, after pharmaceutical company Accord Healthcare "agreed to apply for the licence on a not-for-profit basis".

The move to make anastrozole available to eligible women "represents a potential new frontier in the fight against Britain's big killers", said The Guardian's health policy editor Denis Campbell.

NHS boss Pritchard said the programme could "help us realise the full potential of existing medicines in new uses to save and improve more lives".

The move "adds to the NHS's armoury of preventative breast cancer medication", said Sky News, with tamoxifen and raloxifene already licensed to prevent the disease. 

If even 25% of eligible women take anastrozole, about 2,000 cases of breast cancer a year could be prevented in England, saving the NHS £15 million in treatment.

It is a "major step forward", said Baroness Delyth Morgan, chief executive at charity Breast Cancer Now.

Who is eligible?

Women who have a moderate or high risk of breast cancer are eligible for the medication. For example, a woman whose "first-degree relative (mother, daughter or sister) was diagnosed with breast cancer before the age of 40 is likely to be considered for it", explained Donnelly. 

Those with two such relatives getting breast cancer – at any age – "could also be considered", as would those with "a mix of first and second-degree relatives (such as an aunt, grandparent or niece)". 

"Approaches to help prevent breast cancer at high risk are badly needed," Dr David Crosby, head of prevention and early detection at Cancer Research UK, told The Guardian. This is "a welcome announcement".