17 December 2019

Research presented at the San Antonio Breast Cancer Symposium has shown that the preventative effects of anastrozole, given to some women at high risk of developing breast cancer, last for over five years after women stop taking it.

The researchers suggest that because of this lasting effect anastrozole may be more effective than tamoxifen at preventing oestrogen receptor positive breast cancer in postmenopausal women at an increased risk of the disease.

The IBIS-II trial focused on 3,864 women who were considered to have a high risk of developing breast cancer. For five years, half of these women were given the preventative drug anastrozole and half were given a placebo pill, which has no biological effect. Researchers then followed women for an additional five years and found that those who were taking anastrozole were 50% less likely to have developed breast cancer.

Anastrozole is currently recommended in the NICE guidelines as a preventative therapy for postmenopausal women who are at an increased risk of breast cancer, however the researchers think that the drug is not currently offered to all the women who could benefit from it.

Baroness Delyth Morgan, Chief Executive at Breast Cancer Now, the research and care charity, said:

These major findings could be really important in helping [postmenopausal] women at high risk of breast cancer to decide whether anastrozole is the right option for them.

It’s really encouraging to see that the preventive effects of this drug continue for over five years after women stop taking it, and we hope new information on its long-term benefits will help women to weigh up the pros and cons of this option.

With around 55,000 women being diagnosed each year in the UK, we urgently need to do all we can to prevent more breast cancers. For some women with a family history, risk-reducing drugs like anastrozole can be so important in preventing the disease, but the decision to take preventive therapy can be extremely difficult as it can also come with some unpleasant side effects.

With the option of anastrozole being recommended in clinical guidelines, it is worrying to hear that it may not be being offered to all that could benefit and we need to understand the extent of this potential issue. It’s essential that we raise awareness of this option among doctors and patients, and ensure that all eligible women are given the information and support they need to weigh up its benefits and risks, alongside other risk-reducing options. We’d encourage anyone who is worried about their breast cancer risk to speak to their GP, or to call our free Helpline on 0808 800 6000. Our nurses are just at the end of phone.