The aromatase inhibitor anastrozole has been approved by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) as a preventative treatment for breast cancer in postmenopausal women at moderate or high risk of developing the disease.
Previously authorised for the treatment of breast cancer in postmenopausal women, the drug has been used off-label for prevention and is now approved for this indication.
Anastrozole, which is off patent, is taken as a 1mg tablet, once a day for five years. It works by blocking the aromatase enzyme and reducing the amount of oestrogen that a patient’s body makes.
The most common side effects are hot flushes, feeling weak, pain or stiffness in the joints, arthritis, skin rash, nausea, headache, osteoporosis and depression.
According to Cancer Research UK, the entire five-year course of treatment now costs just £78, or around 4p a day.
Anastrozole was first recommended as a preventive option by the National Institute for Health and Care Excellence (NICE) in 2017, however, with the treatment being unlicensed in this use, uptake has remained low.
NHS England said around 289,000 women at moderate or high risk of breast cancer could be eligible for the drug. It estimated that if 25% of these women chose to take the drug, approximately 2,000 cases of breast cancer could potentially be prevented in England.
This would save around £15m in treatment costs, NHS England said.
NHS 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.
‘Allowing more women to live healthier lives, free of breast cancer is truly remarkable, and we hope that licensing anastrozole for a new use today represents the first step to ensuring this risk-reducing option can be accessed by all who could benefit from it.’
The MHRA approval is based on the International Breast Cancer Intervention Study II (IBIS-II) study – an international, randomised double-blind, placebo-controlled trial.
The results showed a significant continuing reduction in breast cancer with anastrozole in the post-treatment follow-up period, and fewer women developed breast cancer in the anastrozole group compared to the placebo group.
After a median follow-up of 131 months (IQR 105–156), a 49% reduction in breast cancer was observed for anastrozole (85 vs 165 cases, hazard ratio 0.51, 95% CI 0.39–0.66, p<0.0001). The reduction was larger in the first five years (35 vs 89, 0.39, 0.27–0.58, p<0.0001), but still significant after five years.
Anastrozole is the first medicine to be repurposed through the new Medicines Repurposing Programme, which looks at using existing medicines in new ways to benefit patients and the NHS. It is hosted by NHS England and supported by the Department of Health and Social Care, the MHRA, NICE and the National Institute for Health and Care Research.
The licensing work was undertaken by Accord Healthcare on a not-for-profit basis, after Accord Healthcare was selected through an open competitive process. The Medicines Repurposing Programme will now work with the MHRA and the British Generic Manufacturers Association to ensure other companies that make anastrozole adopt the new licensed indication.
Dr David Crosby, head of prevention and early detection at Cancer Research UK, said: ‘Repurposing therapeutic drugs that have already been shown to be safe for prevention is an area with a lot of potential.
‘More research will be key to finding more opportunities like this, to better understand who is at a high risk of getting cancer, and to help lower that risk.’
