New data suggest tamoxifen may no longer offer women the best chance of remaining free from their breast cancer

This is likely to be received as good news by the thousands of women who are currently taking tamoxifen and may be concerned about either the side effects or the effectiveness of this older therapy. Following surgery to remove a breast tumour, women are usually given a hormonal treatment for five years to help prevent the breast cancer from returning – this is known as ‘adjuvant’ therapy. Whilst revolutionising the treatment of breast cancer when it was launched, tamoxifen is unfortunately associated with a number of serious and even life-threatening side effects such as endometrial cancer, deep vein thrombosis and stroke.

In 2001, the first results of a 9,300 patient clinical trial comparing tamoxifen with a newer drug, anastrozole, were published. These results showed that, in postmenopausal women newly diagnosed with breast cancer (i.e. those who were not already taking a hormonal treatment), anastrozole was more effective than tamoxifen in preventing the return of the cancer and was less likely to result in serious side effects. Since then, many women have been prescribed anastrozole instead of tamoxifen as adjuvant therapy when they are first diagnosed with early disease.

There remains, however, a large number of women who were prescribed tamoxifen before these results became available and are now part way through their recommended five-year treatment course. Until now, there has been no evidence to indicate whether they would be better off changing their therapy to the newer drug or whether they should continue to take tamoxifen. These latest trial results may begin to provide the answer. The early findings from the ITA (Intergruppo Tamoxifen Arimidex) study, involving 449 Italian patients, show that women who change their therapy from tamoxifen to anastrozole appear more likely to stay free of the disease for longer and less likely to suffer from a serious drug-related side effect.

Tamoxifen was introduced over twenty-five years ago and has long been regarded as the best hormonal treatment option available to women for this purpose. However times change and new therapies become available, offering patients new treatment choices. Speaking to this point, Professor Jeffrey Tobias, University College Medical School and University College Hospitals, London commented: "Emerging data from trials of anastrozole are now questioning whether tamoxifen remains the best possible treatment for postmenopausal women with hormone sensitive, early breast cancer. Anastrozole has now been shown to have benefits over tamoxifen in at least two different treatment settings - for newly diagnosed patients and those already receiving tamoxifen. Since the best choice for each individual patient may be different, patients are recommended to discuss with their physicians what is the right choice for them."

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Global PR Manager, Oncology, AstraZeneca
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Email: Alison.K.Wright@astrazeneca.com

Anastrozole – marketed as ‘Arimidex’ – is approved world-wide for postmenopausal women with advanced disease. The drug is also already approved as an adjuvant treatment for postmenopausal women with hormone receptor-positive early breast cancer in 25 countries including the US, UK, Germany, Italy, Spain.
Anastrozole is a potent, highly selective, non-steroidal oral aromatase inhibitor used in the hormonal (endocrine) treatment of breast cancer in postmenopausal women.
Tamoxifen is an anti-oestrogen and acts primarily to prevent oestrogen binding to its receptor at tumour sites. Tamoxifen has some partial oestrogenic activity, which may be responsible for the differences in its side-effect profile compared with anastrozole.
Anastrozole acts differently to tamoxifen by blocking the production of oestrogen by the aromatase enzyme pathway – the primary source of oestrogen in postmenopausal women, whose ovaries no longer function.
The current treatment strategy for hormone-sensitive early-stage breast cancer (cancer that has not spread beyond the breast) in postmenopausal women generally consists of initial surgery to remove the tumour, which may be followed by a course of chemotherapy and/or radiotherapy. Women will usually then go on to take a hormonal drug treatment — such as tamoxifen or anastrozole— for around five years to reduce the risk of the cancer recurring (this is known as “adjuvant therapy”).
AstraZeneca continues its tradition of research excellence and innovation in oncology that led to the development of its current anti-cancer therapies including ‘Arimidex’ (anastrozole), ‘Casodex’ (bicalutamide), ‘Faslodex’ (fulvestrant), ‘Nolvadex’ (tamoxifen), ‘Zoladex’ (goserelin) and ‘Tomudex’ (raltitrexed) as well as a range of novel targeted products such as anti-proliferatives, anti-angiogenics, vascular targeting and anti-invasive agents. AstraZeneca is also harnessing rational drug design technologies to develop new compounds that offer advantages over current cytotoxic and hormonal treatment options. The company has over 20 different anti-cancer projects in research and development.
AstraZeneca is a major international healthcare business engaged in the research, development, manufacture and marketing of prescription pharmaceuticals and the supply of healthcare services. It is one of the top five pharmaceutical companies in the world with healthcare sales of over $17.8 billion and leading positions in sales of gastrointestinal, oncology, cardiovascular, neuroscience and respiratory products. AstraZeneca is listed in the Dow Jones Sustainability Index (Global and European) as well as the FTSE4Good Index.