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Anastrozole: Repurposed drug could prevent thousands of breast cancer cases

BMJ 2023; 383 doi: https://doi.org/10.1136/bmj.p2608 (Published 07 November 2023) Cite this as: BMJ 2023;383:p2608
  1. Elisabeth Mahase
  1. The BMJ

Hundreds of thousands of women in England deemed at increased risk of breast cancer could soon be offered anastrozole, after the medicines regulator approved the drug for prevention.

Anastrozole is authorised for treating breast cancer in postmenopausal women and has been used off label in some cases for prevention, but it has now received official approval for prevention in postmenopausal women at moderate or high risk of developing the disease. In trials anastrozole has been shown to reduce the incidence of breast cancer in this population by almost 50%.

NHS England said that if 25% of the estimated 289 000 eligible women chose to take the drug around 2000 cases of breast cancer could be prevented in England and the NHS could save around £15m in treatment costs.

Previous NICE guidance suggested that this preventive treatment would be initiated in secondary or tertiary care,1 although the NHS England announcement provided no details on how this drug will be offered to people at risk.

The Medicines and Healthcare Products Regulatory Agency’s approval was based on the findings of the international randomised controlled trial Ibis-II, which showed that fewer women in the anastrozole group developed breast cancer than in the placebo group.2 The drug is taken as a 1mg tablet, once a day for five years.

Anastrozole works by inhibiting the enzyme aromatase, thereby reducing the amount of oestrogen produced. The most common side effects are hot flushes, feeling weak, pain or stiffness in the joints, arthritis, skin rash, nausea, headache, osteoporosis, and depression.

Delyth Morgan, chief executive of charity Breast Cancer Now, said the approval was a “major step forward that will enable more eligible women with a significant family history of breast cancer to reduce their chance of developing the disease.”

Repurposing drugs

Anastrozole gained its new indication through the multiagency medicines repurposing programme, which was launched in 2021 with the aim of identifying ways that existing drugs could be used to treat different conditions.

NHS England chief executive Amanda Pritchard said, “This is the first drug to be repurposed through a world leading new programme to help us realise the full potential of existing medicines in new uses to save and improve more lives on the NHS. Thanks to this initiative, we hope that greater access to anastrozole could enable more women to take risk reducing steps if they’d like to, helping them live without fear of breast cancer.”

MHRA chief executive June Raine added, “The MHRA welcomes applications for repurposed medicines and encourages early dialogue from companies or developers considering this.”

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