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Anastrazole as Breast Cancer Prevention Treatment

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 4 minutes read

Breast cancer is the most common form of cancer in the UK and every year 55,000 women are diagnosed with it. Currently the process involved screening and then only once, diagnosed they are treated. Unfortunately, around 11,500 will die from the disease every year and the vast majority of cases of breast cancer are diagnosed after the age of 50.

One of the most common treatments used in breast cancer is called anastrozole – a hormone that is given as a daily tablet. This is because some breast cancers need the hormone oestrogen to grow, and an enzyme called 'aromatase' is needed for this change to occur. Anastrozole works by blocking (inhibiting) this enzyme, which in turn reduces the amount of oestrogen in your body, which slows the growth of breast cancer cells.

Under new plans just announced by the NHS, up to 300,000 women who are said to be at moderate or high risk of developing breast cancer will now be offered anastrozole as a preventive treatment in order to reduce their risk of breast cancer occurring in the first place. It has been estimated that if this roll-out is taken up in full, it could prevent 8,000 cases of breast cancer among women currently in their 50s and 60s if taken for a full 5-year course.

Anastrozole has been licensed for the treatment of breast cancer since 2006, but until now has not been licensed as a preventive treatment.

Who is eligible for anastrozole for the prevention of breast cancer?

Any post-menopausal woman with a mother or sister diagnosed with the disease before the age of 40, or those with two close relatives with breast cancer at any age, are encouraged to come forward to their doctor for assessment. If suitable, their GP is able to prescribe anastrozole.

Women have a one in seven chance of developing breast cancer but are said to be at moderate risk if this increases to around one in six. Women are said to be at high risk if this increases further to at least one in three.

Why is anastrozole now being used as preventive treatment?

Trials have shown that women at high risk of breast cancer who took anastrozole for five years saw their risk fall by 49% for more than a decade. The ‘at-risk’ group of women and breast cancer in the UK amounts to 4% of all women aged between 50 and 69.

Anastrozole is a generic medication which means it is a cheap treatment, costing the NHS around 4 pence a day. It is a simple tablet treatment, taken once a day for five years.

What are the side effects of anastrozole?

As with any medication, anastrozole has the capacity to cause side effects but this varies significantly from person to person. The commonly reported side effects of anastrozole include:

Although these unwanted effects can often settle over time as your body adjusts to the medication, if they continue or become troublesome then speak with your doctor or pharmacist.

Who should not take anastrozole?

It should not be used in premenopausal women, and should be used with care in women who are prone to osteoporosis.

How is anastrozole taken?

It is taken as a once daily tablet, typically 1mg a day for 5 years for breast cancer prevention, and for variable durations in the treatment of breast cancer. It can be taken with or without food at any time but it is best if it is taken at the same time every day. If you miss a dose, you don’t need to take an extra dose the next day as the level of the drug in your body stays high enough to work from taking it the day before. 

How is anastrozole being rolled out in the UK as a preventive treatment?

It is being used under the NHS England ‘repurposing’ programme, where drugs that are licensed for one use – such as treating breast cancer – can be approved for another – such as breast cancer prevention – if they are found to be effective. This is a similar programme to that used during the COVID-19 pandemic where drugs such as steroids and common arthritis treatments were repurposed to help treat it.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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