Long term study of Breast Cancer drugs confirms benefit

Around 32,000 postmenopausal women are diagnosed with breast cancer every year in the UK, and so long term trial results are important.

There are different types of breast cancer that can be identified by their ability to attach the hormone oestrogen and therefore classified as oestrogen positive (ER positive). The cancer in these patients is driven by the hormone oestrogen attaching to oestrogen receptors on the breast cancer cells. These tumours are normally treated with hormonal therapy such as tamoxifen or anastrozole. However, if a breast cancer involves cells which do not have oestrogen receptors i.e. it is ER negative, the patient will usually be advised to have chemotherapy instead. Both anastrozole and tamoxifen work by interfering with the female hormone oestrogen, which is known to be the most important cause of breast cancer.

A major international trial has confirmed the long-term benefit of anastrozole to help stop breast cancer coming back or developing in the other breast in postmenopausal women with hormone sensitive early breast cancer, according to a study published in Lancet Oncology today. The trial was led by Professor Jack Cuzick, Cancer Research UK epidemiologist based at Queen Mary, University of London and is the longest ever follow up of a particular class of drugs called aromatase inhibitors. These replaced tamoxifen as the gold standard hormone treatment in 2009, following earlier trial results showing they are the best treatment for preventing breast cancer recurrences in women who have gone through the menopause.

Professor Cuzick said: “Tamoxifen has been in use for at least 25 years and remains one of the most effective breast cancer treatments ever developed. But these results provide further support for using anastrozole as the first line treatment for postmenopausal women with hormone sensitive breast cancer, as it’s even more likely to stop the disease coming back and was better tolerated than tamoxifen.”

Kate Law, Cancer Research UK's director of clinical research, said: “Drugs like tamoxifen and now anastrozole have made a significant contribution to the impressive survival rates we see for breast cancer today by cutting the risk of the disease coming back.

“Anastrozole is one of three aromatase inhibitors currently prescribed to help prevent breast cancer coming back in postmenopausal women – the highest risk group. But all drugs have side-effects and it’s essential we continue to monitor the long-term performance of these drugs before we can conclusively say which is the safest and best option for this group of women.”

Further information on breast cancer: see Prof Kefah Mokbel.