Anastrozole should be the preventive drug recommended for post-menopausal women at increased risk of developing breast cancer, according to the findings of a new international study today.
Professor Jack Cuzick of Queen Mary University of London, who led the research, said the drug was more effective than tamoxifen.
Anastrozole inhibits the production of oestrogen in postmenopausal women and has been used to treat breast cancer in that cohort for more than 20 years.
The first phase of the study confirmed it as a prophylactic therapy, with breast cancer occurrence among women taking the drug falling by 53%.
And although it was recommended for preventive use in the UK by the drug advisory body NICE in 2017 and by the US Preventive Services Task Force earlier this year, it is not offered to all the women who could benefit, possibly because of the evidence surrounding long-term impact.
Writing in The Lancet, Professor Cuzick says anastrozole offers significant long-term protection for women who take it for five years and stop.
His team found breast cancer incidence was 49% lower in women who had taken the drug compared to women who received a placebo up to seven years after the trial stopped. It was also significantly higher than the 28% decrease in breast cancer recorded for women who take tamoxifen.
Professor Cuzick, who is co-chairman of International Breast Cancer Intervention Studies (IBIS), presented the findings of the IBIS-II trial at the San Antonio Breast Cancer Symposium in Texas yesterday (12 December 2019).
He 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.”
The study also records that anastrozole does not have the same type of long term side-effects, including endometrial cancer and no increase in fractures or heart disease, associated with tamoxifen.
The researchers also found a 39% reduction in skin cancer among women who had taken anastrozole – a finding Prof Cuzick says is yet to be understood.
Cuzick J, Sestak I, Forves JF et al. Use of anastrozole for breast cancer prevention (IBIS-II): long-term results of a randomised controlled trial. The Lancet 13 December 2019.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)32955-1/fulltext
Leave a Reply