Breast cancer drug Anastrozole offers protection for at least 12 years
In collaboration with
- Ivana Sestak Reader in Medical Statistics
- Professor John F Forbes Emeritus Professor, Newcastle University
- Professor Mitch Dowsett Team Leader, The Institute of Cancer Research
- Mr Simon Cawthorn Breast Care North Bristol NHS trust
- Professor Robert Mansel Emeritus Professor of Surgery at Cardiff University
- Professor Dr Sibylle Loibl Head of the German Breast Group
- Dr Bernardo Bonanni Director Cancer Prevention European Institute of Oncology
- Professor Gareth Evans Genetics, Cancer Epidemioligy University of Manchester
- Professor Anthony Howell Chair in Breast Oncology, University of Manchester
Postmenopausal women at high risk of breast cancer took Anastrozole for five years. Twelve years after they first took the drug, these women exhibited breast cancer incidence 49% lower than women given a placebo.
The 49% reduction is significantly higher than the 28% decrease in breast cancer recorded for women who take Tamoxifen, a hormone therapy which is sometimes used in women who have a high risk of breast cancer, to prevent breast cancer from developing.
The latest report also confirms that Anastrozole does not have the same type of long term side effects associated with Tamoxifen, including endometrial cancer and blood clots.
The research was funded by AstraZeneca, Cancer Research UK and the National Health and Medical Research Council Australia.
A long-term research project
The study focused on ductal carcinoma in situ (DCIS), 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’s 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.
Dr Cuzick 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.”
What does Anastrozole do?
Anastrozole inhibits the production of oestrogen in postmenopausal women. The first phase of this study, published in 2013, established its value as a prophylactic therapy. It reported that breast cancer occurrence among women taking the drug fell by 53%.
The most recent study, published in The Lancet, confirmed the drug offers significant long-term protection for women who take it for five years and stop.
The research team recorded data on the women’s health over a 12-year period, with a median follow-up of 10.9 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.”— Professor Jack Cuzick
How might Anastrozole change treatment going forward?
Professor Cuzick said: “This exciting finding makes a strong case for Anastrozole being the drug of choice for post-menopausal women at high risk of developing breast cancer. Previous research 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.”
The latest report also confirms that Anastrozole does not have the same type of long term side-effects associated with Tamoxifen.
Clinical lead Professor Tony Howell from the University of Manchester said: “Importantly, this study shows that there are no significant long term side-effects in the five years after completion of anastrozole, particularly no increase in fractures or heart disease.”
What is the future for patients on Anastrozole?
Professor Cuzick said that with few deaths from breast cancer among trial participants, longer follow-up will be needed to evaluate whether Anastrozole can reduce deaths from the disease.
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. Hopefully the newest study may encourage more physicians to offer this effective treatment to at-risk patients.
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