Health & Lifestyle

What is anastrozole? What are the side effects? And am I eligible for the breast cancer drug? All your questions answered

Women with a higher risk of developing breast cancer are set to be offered a pill that cuts their risk of developing the disease in half. 

NHS England and UK medication watchdogs announced the pill anastrozole will now be offered as a cancer preventative thanks to a new approvals process that repurposes old drugs for new uses. 

The health service’s chief executive, Amanda Pritchard, said: ‘It’s fantastic that this vital risk-reducing option could now help thousands of women and their families avoid the distress of a breast cancer diagnosis.’

Women already taking the drug have described it as a ‘gift’ that allows them to go about their lives with less worry about a potential cancer diagnosis.

But what exactly is anastrozole? Who is eligible? And are there any side effects?

Here, MailOnline answers all your questions…

Traditionally, anastrozole has been used as a treatment for women suffering with breast cancer. But trials have found the hormone therapy can also slash a woman's chances of developing it by half

Traditionally, anastrozole has been used as a treatment for women suffering with breast cancer. But trials have found the hormone therapy can also slash a woman’s chances of developing it by half

What is anastrozole and how does it work?

Anastrozole is a hormone therapy medication that has been used for years in treating breast cancer.

It works by reducing the amount of aromatase the body can produce. After women go through the menopause, this enzyme is vital for oestrogen production.

This reduces the risk of breast cancer, as oestrogen fuels the growth of some versions of the disease.

What has happened?

While anastrozole has been used as breast cancer medication for years, doctors can now easily prescribe it as a cancer preventative.

The drug’s preventative benefits have been known since 2017.

However, hurdles had to be overcome before it could be offered for this use.

After AstraZeneca‘s patent on anastrozole expired it became a generic medication, meaning it could be made by any drug manufacturer — a process that usually sees drugs become cheaper.

However, it also leaves little incentive for companies to go through the steps of getting a generic medication approved for another medical use — in this case, cancer prevention rather than treatment.

However, Britain’s Medicines Repurposing Programme, which was set up in 2021 by the NHS, Government and UK drug and treatment watchdogs, takes on this process.

A small number of women were previously prescribed the drug as a cancer preventive ‘off-label’, meaning doctors were prescribing it outside of its officially approved use.

But the new official approval is expected to make it easier for more women to get hold of it, with NHS chiefs saying around 289,000 women will be eligible.

How effective is it a preventing cancer? 

Breast cancer cases fell by 49 per cent among women at high risk of developing breast cancer who took anastrozole, according to clinical trials.

The study followed 4,000 post-menopausal women for 10 years and found that the reduced risk of breast cancer remains, even when women stopped taking the drug.

Breast cancer is most commonly diagnosed in women over the age 50 who have been through the menopause, accounting for 80 per cent of all cases in the UK. 

How often do patients have to take it?

Anastrozole is taken as a daily tablet. 

Women prescribed the drug for breast cancer prevention will take it for five years between the age of 50 and 69.

Who will be eligible for the medication?

The NHS says around 289,000 women with either a moderate of high risk of breast cancer aged between 50 and 69 could be eligible for the drug.

Women will be classed as moderate risk if they have one close relative, such as a mother, sister or daughter, who has breast cancer.

Their risk of developing the disease is around one in six, compared to one in seven among the general population. 

Women are considered as high risk if two close relatives or one close relation and a second more distant relative — such as a grandmother or aunt — have breast cancer.

Their chance of developing the disease is one in three.

It is expected that women will be offered anastrozole after seeing their GP, who will look at their family history. However, this process could involve a further consultation with a specialist.

What are the side effects?

The most common side effects are menopause-like symptoms.

More than one per cent of women taking the medication will suffer hot flushes, difficulty sleeping, tiredness and low mood, as well as a dry or itchy vagina, mild aches and pain and hair thinning or loss.

However, these side effects usually improve within the first few months of taking anastrozole.

Serious side effects occur in fewer than one in 100 women taking the drug. These include painful or swollen muscles and joints, liver problems and blurry eyesight.

How many lives could it save?

There are no specific estimates for this.

But the NHS says that even if only a quarter of eligible women take up the offer of the medication it will prevent 2,000 cases of breast cancer.

While not all of these would necessarily be fatal, it will save these women from having to treatments such as surgery or gruelling chemotherapy. 

Breast cancer kills about 11,500 Brits per year, making it the fourth biggest cancer killer in the UK. 

For women specifically, breast cancer is second biggest cause of death of all versions of the disease. 

Why does the NHS think not all women eligible for it will take the medication? 

This is likely due to the side effects. 

Some women will be more susceptible to them than others, or suffer more severe symptoms while taking the drug, so may opt to stop taking it.

Additionally, as anastrozole is a cancer preventative, there will be no proof for a woman taking the drug that it has stopped them from developing breast cancer.

Considering that even a woman at a high risk of developing breast cancer has a higher chance of dodging the disease than receiving a cancer diagnosis, some women may decide that taking the medication for five years isn’t worth it. 

How much does the drug cost? 

Anastrozole costs just 4p per tablet, meaning a five-year course totals £70. 

It would cost £5.3million for 72,250 women to take the medication for five years. 


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