Anastrozole reduces breast cancer rates long term

Researchers have found that the Anastrozole drug has cut the risk of breast cancer in half and protected women for seven years after they stopped taking it.

Jack Cuzick, the Queen Mary University of London professor who is leading an international breast cancer study says anastrozole – rather than tamoxifen – should be the preventive drug-of-choice for post-menopausal women at increased risk of developing the disease.

The drug, which inhibits the production of oestrogen in postmenopausal women, has been used to treat breast cancer in that group for more than 20 years. Previous studies of the drug in 2013 found that breast cancer occurrence amongst women taking the drug fell by 53 per cent, after which it was recommended for preventive use by the National Institute for Health and Care Excellence in the UK in 2017 and by the US Preventive Services Task Force earlier this year.

However, the drug is not currently offered to all the women who could benefit – possibly because some physicians are unsure of the evidence base for long term impact.

The latest study, published in The Lancet, has confirmed that the drug offers significant long term protection for women who take it for five years and stop, with research finding that breast cancer incidence was 49 per cent lower than in women given a placebo up to seven years after trial participants last took the drug.

Cuzick said: “Previous research has confirmed that anastrozole is very effective while women are still taking the drug but this is the only trial looking at whether it offers long term protection for women at high risk of developing breast cancer. After a detailed analysis of the IBIS-II data, we have concluded that it is highly effective in reducing breast cancer occurrence for at least 12 years.

“This is an exciting finding which makes a strong case for anastrozole being the drug of choice for post-menopausal women at high risk of developing breast cancer. Tamoxifen could be offered to the relatively few women who experience serious side-effects from anastrozole.”

Charles Swanton, Cancer Research UK’s chief clinician, said: “Both tamoxifen and anastrozole can be given to women who are at higher risk of breast cancer. Up until now we only knew that tamoxifen has long lasting benefits, so it’s reassuring that this study looking specifically at anastrozole, which has fewer long term side-effects, gives better protection to women years after they stopped taking the drug.

“Doctors may still decide that tamoxifen is more appropriate for some women, but it’s great that there are options. Anyone with questions about these findings, or about their family history and risk of breast cancer, should speak to their doctor, who can help work out which medication is best for them.”