190122 breast cancer awareness
In trials, anastrozole has been shown to reduce instances of the disease in most post-menopausal women by almost 50%. Image Credit: Supplied

London: Anastrozole, a daily pill to prevent breast cancer, will now be available to thousands of more women in the UK after being cleared for wider use.

The drug has been used to treat hormone-driven breast cancers for years in England, but was not previously licensed for prevention. In trials, anastrozole has been shown to reduce instances of the disease in most post-menopausal women by almost 50%.

The new licensing regime has the potential to prevent thousands of cases. Breast cancer is the most common type of cancer in the UK, according to the NHS. Around one in seven women "- most over the age of 50 "- will get the disease in their lifetime.

So what is anastrozole, and why has its licensing changed? Does anastrozole have any side effects? We answer some common questions below.

What is anastrozole?

Anastrozole is a drug used to both treat and prevent hormone-driven breast cancers. It works by reducing the amount of estrogen the body can make by blocking an enzyme called aromatase. By lowering estrogen levels, it can minimise the growth of hormone-driven breast cancers. Because of its effects in changing hormone levels, it is largely used with women who have been through menopause. It can also be given to men with breast cancer.

It comes as a 1mg pill that is taken daily. The NHS recommends taking it at the same time every day, and it must be taken for five years.

Its disease-prevention effects have been known for at least a decade, when a global clinical trial first proved fewer women developed breast cancer when taking the medicine.

Who can take anastrozole? When and why has this changed?

Currently, the drug is used as part of cancer treatment. It was also recommended as a cancer prevention drug by the National Institute for Health and Care Excellence in 2017, though its uptake has been low until now.

The Medicines and Healthcare products Regulatory Agency (MHRA) just signed off on it as a preventive treatment too, meaning the NHS will offer the drug to around 289,000 women who are at higher risk of cancer.

Women will be judged to be at-risk if they have a "significant" family history of the disease, and if they have already passed the menopause. 

The NHS doesn't expect every eligible person to take it. With the uptake of the drug, the NHS estimated about 2,000 cases of breast cancer could be prevented in England and it could lead to a saving of Pound15 million in overall treatment costs.

Amanda Pritchard, chief executive of the NHS called the drug a "vital risk-reducing option could now help thousands of women and their families avoid the distress of a breast cancer diagnosis." She added that anastrozole is the first drug in a "world-leading" new strategy of repurposing current drugs in other uses to save lives.

Does anastrozole have side effects?

The most common are ones that are similar to menopause, including hot flushes, depression, osteoporosis, tiredness, difficulty sleeping, nausea, vaginal dryness and thinning hair. The NHS says that these are most common in the first few months of taking the drug and usually improve after then.

It's not recommended for women who are pregnant, breastfeeding, or trying to conceive.

What are the long-term effects of taking anastrozole?

Estrogen is crucial for maintaining bone strength, which means that long-term use of anastrozole can make bones more likely to break. Patients taking anastrozole must therefore go for bone density scans one or two years into and after treatment. Women taking it might have to add additional medicine to reduce the risk of bone damage and increase strengthening exercises.

Anastrozole can also increase blood pressure and cholesterol, which may require additional treatment.