30% women fail to respond to cancer drug

SCIENTISTS now know why one in three women fail to respond to a leading breast cancer treatment.

About 30% of breast cancers do not respond to the drug tamoxifen which is used to treat thousands of Irish women.

Scientists at Cancer Research UK have now found a “key chemical switch” in breast tumours that resist the drug.

They are now developing a testing procedure which would enable doctors to predict the effectiveness of tamoxifen for individual patients.

Interim chief executive of Cancer Research UK, Sir Paul Nurse, said the development of tamoxifen was a crucial step forward for breast cancer treatment. While it was effective for many women, it did not work for everyone.

Nurse said that by identifying those women who won’t respond to the drug doctors can explore other avenues of treatment more rapidly.

Consultant oncologist at St Vincent’s Hospital in Dublin, Dr John Crown, said patients whose disease is resistant to tamoxifen obviously presented difficult challenges.

Hormone therapy remained the essential component in breast cancer treatment, he said, but if the new scientific data was confirmed it could allow the treatment to be improved.

“Tamoxifen has been a phenomenally successful drug over the years,” said Dr Crown.

“Although newer drugs have emerged that offer advances over it, tamoxifen is still a key component in breast cancer treatment.”

Tamoxifen, which has been in use in Ireland since the 1970s, is designed to counteract the effects of oestrogen.

The treatment improves the chances of survival of women with oestrogen-receptive positive breast cancers.

About 50% of breast cancers are oestrogen-receptive and about 70% are successfully treated with the drug.

The UK scientists who worked on 14 biopsy samples found that when the treatment was unsuccessful, part of the oestrogen receptor molecule was chemically altered, a state in which it became immune to the inhibitory effects of tamoxifen.

The discovery will help to identify women who are not going to respond to the drug so that other ways of treating them can be explored.

At the moment, the system for monitoring tamoxifen treatment is relatively primitive.

Breast cancer statistics

Ireland has the third highest death rate from breast cancer in the EU.

There are about 650 deaths from breast cancer annually.

Breast cancer is very treatable if detected early.

A mammogram (a breast X-ray) can pick up changes in the breast before they can be seen or felt.

The BreastCheck freephone info line is free phone [phone].

The Action Breast Cancer Helpline (a project of the Irish Cancer Society) is free phone [phone].