Scientists unravel resistance to breast cancer treatment

Scientists have identified a molecular flag in women with breast cancer who do not respond or have become resistant to the hormone drug tamoxifen.

Tamoxifen, used alongside traditional chemotherapy and radiotherapy, blocks the female hormone oestrogen that, in certain breast cancers, is required by the tumour to grow; it has been shown to improve cancer survival rates by up to one third.

However, about one third of patients with the appropriate type of breast cancer – known as oestrogen receptor positive breast cancer – do not respond to tamoxifen or develop resistance to the drug.

Oestrogen receptor positive breast cancer is the most common form of the disease accounting for 70 per cent of cases.

Now, a team from the University of Manchester's Paterson Institute for Cancer Research has identified a molecular flag that will help doctors predict which patients will respond best to complementary (adjuvant) hormone therapy with tamoxifen.

''The identification of molecular flags to classify subgroups of breast cancer and so determine the best treatment for each patient is of increasing importance in cancer therapy,'' said study lead Professor Göran Landberg.