Alternative to tamoxifen may be preferable for women with early signs of breast cancer

In collaboration with the Press Association

UK research has suggested that the drug anastrozole could be a new option for some post-menopausal women with DCIS – a condition where cancer-like changes develop in cells of the breast.

"This trial shows that there is an equally good alternative in anastrozole, which may suit some people better" - Professor Peter Johnson, Cancer Research UK

Results from the Cancer Research UK-funded IBIS-II DCIS trial, run by researchers at Queen Mary University of London (QMUL), suggest the drug is as effective as tamoxifen in preventing cancer in women with the condition.

Anastrozole is already used to treat breast cancer itself, but until now there has been little research into using the drug to treat DCIS. Tamoxifen is the standard treatment for the disease.

DCIS affects around 6,400 women every year. If left untreated, in some women it can start to spread into the surrounding breast tissue after some years, and eventually develop into cancer. 

Cancer Research UK’s chief clinician Professor Peter Johnson said the trial result showed that an “equally good alternative” to tamoxifen had been unearthed, with the potential to better target certain patients depending on their susceptibility to side effects.

"Breast cancer is the single most common cancer in the UK and we continue to learn more about how to prevent and treat it through our research,” he said. “We already know that tamoxifen can reduce the risk of cancer developing in some women who have early changes in the breast, but some get unacceptable side effects.

“This trial shows that there is an equally good alternative in anastrozole, which may suit some people better. It's important we continue to gain more insight into the side effects of different drugs and understand who is at higher risk and who is most likely to benefit."

The study is published in The Lancet

In total, 2,980 post-menopausal women from 14 countries, who’d had surgery to remove their DCIS, took either anastrozole or tamoxifen for the following five years. 

After an average follow-up of 7.2-years, 144 of them subsequently developed breast cancer, with similar rates of cancer among women taking either drug. 

However, the two drugs caused different side effects. Women who took anastrozole had fewer deep vein thromboses and gynaecological issues compared to those who took tamoxifen – along with fewer incidences of much rarer side effects such as ovarian, womb and non-melanoma skin cancer.

But anastrozole led to increased rates of gastrointestinal cancers, strokes, fractures and musculoskeletal issues. 

Lead author Professor Jack Cuzick from QMUL, said: "Now we know that anastrozole is effective for treating hormone-sensitive ductal carcinoma in situ, women will have a greater choice of treatments to suit their own previous medical histories and tolerability of medications."


  • Forbes, J F., et al. (2015). Anastrozole versus tamoxifen for the prevention of locoregional and contralateral breast cancer in postmenopausal women with locally excised ductal carcinoma in situ (IBIS-II DCIS): a double-blind, randomised controlled trial The Lancet : 10.1016/S0140-6736(15)01129-0