Switching Drugs Improves Breast Cancer Survival Rates, Long-Term Trial Data Shows

Until recently, most women diagnosed with early stage oestrogen receptor-positive (ER+ or hormone sensitive) breast cancer were given tamoxifen for around five years after surgery to help prevent the disease coming back. This therapy was once viewed as the ‘gold-standard’ treatment and it has been shown to cut the risk of death by 34%. However, over recent years, increasing numbers of these women are treated with aromatase inhibitors either as first-line treatment or after treatment with tamoxifen.

A large-scale trial called the Intergroup Exemestane Study (IES) was set up across 37 countries in 1998 to examine the long-term effectiveness of switching to exemestane after two to three years tamoxifen to complete a total of five years adjuvant treatment. The study is led by The Institute of Cancer Research’s Clinical Trials & Statistics Unit (ICR-CTSU) and Imperial College London’s Clinical Trials Unit – Cancer.  The trial was funded by pharmaceutical company Pfizer Inc and both units receive support from Cancer Research UK.

Postmenopausal patients who were disease-free after two to three years of adjuvant tamoxifen were randomly assigned to continue tamoxifen or switch to exemestane for the remainder of the five-year period. Results published in 2007 showed that women who switched drugs had higher survival rates, however it was unclear whether this effect would continue in the years after treatment finished and whether there would be any long-term side-effects.

The analysis published today includes 4,052 patients with ER+ cancer and 547 women with tumours whose ER status is unknown.  After a median follow-up of 91 months, women who had been switched to exemestane were 18 per cent less likely to have disease recurrence and were 14 per cent less likely to have died than those who stayed on tamoxifen. Women who took exemestane experienced fewer gynaecological side-effects and more musculoskeletal side-effects while on treatment, but there was no significant difference in long-term side-effects between the groups.

Lead author Professor Judith Bliss, Director of the ICR’s Clinical Trials & Statistics Unit, says: “The long-term results from our study show that the improvements observed following the switch to exemestane are real and continue for at least five years after finishing treatment. These modest but persistent improvements in overall survival will be welcome news for the many postmenopausal women diagnosed with ER+ breast cancer.”

Principle Investigator Professor Charles Coombes, Head of Division of Cancer at Imperial College London, says: “At the start of this study we were uncertain as to whether we would encounter long-term side effects or whether any beneficial effects would be outweighed by these side-effects. As a result of this latest analysis, we can be sure that we not only benefit more women, but also that they encounter fewer serious effects such as deep vein thrombosis or uterine cancer while on treatment, when compared to women who stay on tamoxifen treatment for the entire five years.”

About 75 per cent of the 48,000 women diagnosed with breast cancer in the UK each year have an oestrogen receptor positive tumour, meaning that the hormone oestrogen is playing a role in cancer growth. Both tamoxifen and exemestane are hormone treatments: tamoxifen works by blocking the tumour’s ability to use oestrogen, while aromatase inhibitors like exemestane reduce the body’s production of oestrogen.

The researchers believe that during treatment with tamoxifen, some cancer cells can become resistant to the effects of the drug. Exemestane is subsequently able to kill these resistant cells by withdrawing the oestrogen from circulation.

Dr Lesley Walker, Cancer Research UK’s director of cancer information, says: “These results show that exemestane is a valuable addition to the treatment of hormone-positive breast cancer, providing a way of avoiding tamoxifen resistance and improving treatment success and survival for many women. Aromatase inhibitors like exemestane are really improving the options for breast cancer treatment and are showing great promise in the realm of breast cancer prevention too.”



Media Contact: ICR Science Communications Manager Jane Bunce on 0207 153 5106 or after hours 077217 47900


Notes to editors:


The Institute of Cancer Research (ICR)

  • The ICR is Europe’s leading cancer research centre
  • The ICR has been ranked the UK’s top academic research centre, based on the results of the Higher Education Funding Council’s Research Assessment Exercise
  • The ICR works closely with partner The Royal Marsden NHS Foundation Trust to ensure patients immediately benefit from new research. Together the two organisations form the largest comprehensive cancer centre in Europe
  • The ICR has charitable status and relies on voluntary income
  • As a college of the University of London, the ICR also provides postgraduate higher education of international distinction
  • Over its 100-year history, the ICR’s achievements include identifying the potential link between smoking and lung cancer which was subsequently confirmed, discovering that DNA damage is the basic cause of cancer and isolating more cancer-related genes than any other organisation in the world
  • The ICR is home to the world’s leading academic cancer drug development team. Several important anti-cancer drugs used worldwide were synthesised at the ICR and it has discovered an average of two preclinical candidates each year over the past five years.
  • The Institute of Cancer Research’s Clinical Trials and Statistics Unit (ICR-CTSU) is an academic clinical trials unit accredited by the National Cancer Research Institute (NCRI) to conduct clinical trials into cancer treatments. The department is funded by an infrastructure grant from Cancer Research UK.

For more information visit www.icr.ac.uk


Imperial College London

Consistently rated amongst the world’s best universities, Imperial College London is a science-based institution with a reputation for excellence in teaching and research that attracts 14,000 students and 6,000 staff of the highest international quality. Innovative research at the College explores the interface between science, medicine, engineering and business, delivering practical solutions that improve quality of life and the environment – underpinned by a dynamic enterprise culture.

Since its foundation in 1907, Imperial’s contributions to society have included the discovery of penicillin, the development of holography and the foundations of fibre optics. This commitment to the application of research for the benefit of all continues today, with current focuses including interdisciplinary collaborations to improve global health, tackle climate change, develop sustainable sources of energy and address security challenges.

In 2007, Imperial College London and Imperial College Healthcare NHS Trust formed the UK’s first Academic Health Science Centre. This unique partnership aims to improve the quality of life of patients and populations by taking new discoveries and translating them into new therapies as quickly as possible.

Website: www.imperial.ac.uk

About Cancer Research UK

  • Cancer Research UK is the world’s leading cancer charity dedicated to saving lives through research
  • The charity’s groundbreaking work into the prevention, diagnosis and treatment of cancer has helped save millions of lives.  This work is funded entirely by the public.
  • Cancer Research UK has been at the heart of the progress that has already seen survival rates double in the last forty years.
  • Cancer Research UK supports research into all aspects of cancer through the work of over 4,000 scientists, doctors and nurses.
  • Together with its partners and supporters, Cancer Research UK’s vision is to beat cancer.

For further information about Cancer Research UK’s work or to find out how to support the charity, please call 020 7121 6699 or visit www.cancerresearchuk.org