The drug anastrozole is effective in treating an early form of breast cancer, according to a clinical trial led by Queen Mary University of London (QMUL). The results of the IBIS-II DCIS trial show that anastrozole is as effective as tamoxifen for this type of breast cancer and could offer a new treatment option for post-menopausal women.
Ductal carcinoma in situ (DCIS) is described as a very early form of breast cancer, where cancer cells are present in milk ducts, but have not spread to the surrounding breast tissue. It is estimated that approximately a fifth of all screen-detected breast cancers are DCIS, with around 4,800 people diagnosed with DCIS in the UK each year.
Lead author Professor Jack Cuzick from QMUL said: "We found that anastrozole and tamoxifen had similar overall efficacies, with slightly better outcomes for those who took anastrozole. But more importantly, because of their very different side-effects, anastrozole can be offered as an alternative for patients who may not tolerate tamoxifen as well or have previous illnesses making tamoxifen unsuitable.
"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."
The research was funded by Cancer Research UK, and the results are being presented at the 2015 San Antonio Breast Cancer Symposium on 11th November and published in The Lancet.
Professor Peter Johnson, Cancer Research UK's chief clinician, said: "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. 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 looked at 2,980 postmenopausal women with DCIS in 14 countries, who were either given anastrozole or tamoxifen for five years after surgery. After a median follow-up of 7.2 years, 144 participants developed breast cancer, and 69 died, of which four were due to breast cancer.
The groups had a similar number of cases of the disease recurring, whether they took tamoxifen or anastrozole. Those who took anastrozole had an 11 per cent lower rate of recurrence of DCIS or invasive cancer than those who took tamoxifen, but this difference was not significant.
The women in the two groups had different side effects. Women who took anastrozole experienced fewer womb and ovarian cancers and non melanoma skin cancers, and fewer deep vein thromboses and gynecological issues, compared with those who took tamoxifen. However, more strokes, fractures and musculoskeletal issues were seen among those receiving anastrozole.
The trial was limited by its lower-than-expected event rate, which adds uncertainly about the lack of statistical significance of some of the small differences seen. The authors say it is too early to assess the effect of these treatments on mortality, and long-term follow-up and further research is planned to study these issues.
The study was also funded by National Health and Medical Research Council Australia, Breast Cancer Research Fund, and AstraZeneca.
Following on from IBIS-II, the IBIS 3 Feasibility study will begin recruitment in 18 UK sites in January 2016, with the aim of comparing further treatments for 300 breast cancer survivors at high risk of late recurrence.
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Notes to the editor
Press conference and telephone access
A press conference on the research will be held on Friday 11th December 2015 at 13:30 GMT / 07:30 CT at the San Antonio Breast Cancer Symposium in Room 217D of the Henry B. Gonzalez Convention Center. Further details on dialing in from abroad can be provided by contacting Joel Winston.
'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'.
John F Forbes, Ivana Sestak, Anthony Howell, Bernardo Bonanni, Nigel Bundred, Christelle Levy, Gunter von Minckwitz, Wolfgang Eiermann, Patrick Neven, Michael Stierer, Chris Holcombe, Robert E Coleman, Louise Jones, Ian Ellis, Jack Cuzick, on behalf of the IBIS-II investigators The Lancet. 11 December 2015.
About Queen Mary University of London
Queen Mary University of London (QMUL) is one of the UK's leading universities, and one of the largest institutions in the University of London, with 20,260 students from more than 150 countries.
A member of the Russell Group, we work across the humanities and social sciences, medicine and dentistry, and science and engineering, with inspirational teaching directly informed by our research - in the most recent national assessment of the quality of research, we were placed ninth in the UK (REF 2014).
We also offer something no other university can: a stunning self-contained residential campus in London's East End. As well as our home at Mile End, we have campuses at Whitechapel, Charterhouse Square and West Smithfield dedicated to the study of medicine, and a base for legal studies at Lincoln's Inn Fields.
We have a rich history in London with roots in Europe's first public hospital, St Barts; England's first medical school, The London; one of the first colleges to provide higher education to women, Westfield College; and the Victorian philanthropic project, the People's Palace based at Mile End.
QMUL has an annual turnover of £350m, a research income worth £100m, and generates employment and output worth £700m to the UK economy each year.
About Cancer Research UK
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- Cancer Research UK's pioneering work into the prevention, diagnosis and treatment of cancer has helped save millions of lives.
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- Cancer Research UK has been at the heart of the progress that has already seen survival in the UK double in the last forty years.
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