One in three breast cancers change form when they spread, discover Breakthrough Breast Cancer scientists

Scientists from the Breakthrough Breast Cancer Research Unit at the University of Edinburgh analysed 211 tumours which had spread from the breast to the lymph nodes, in the armpit. This is where breast cancer cells usually spread to first. In the largest study of its kind they found that in 82 (39%) cases the disease in the lymph nodes had changed type.

Breast cancer is a complex disease with many different types which can be treated in different ways. Cancer cells that have spread to lymph nodes are often more difficult to treat than those in the breast and so it is vital women receive the most appropriate treatment. Breast cancer spreads to the lymph nodes in about 40%* of the 46,000 women diagnosed with breast cancer in the UK each year.

Researchers were surprised to find the disease changed in such a high proportion of patients, and in so many ways, when it had spread.

For example, 20 tumours changed from oestrogen receptor (ER) negative to ER positive. This change would mean hormone therapies such as tamoxifen, which would not have worked for the original tumour, could help treat the disease if it has spread. Other tumours changed from ER positive to ER negative, which suggests those patients may be given treatments which will not benefit them, and are therefore experiencing side effects unnecessarily.

Lead researcher Dr Dana Faratian, from the Breakthrough Breast Cancer Research Unit at the University of Edinburgh, said: “We were surprised that such a high proportion of tumours change form when they spread beyond the breast. This suggests there is a need to test which type of disease a woman has in the lymph nodes, because it could radically alter the course of treatment she receives. We now need a clinical trial to see how these results could benefit patients.”

Professor David Harrison, Director of the Breakthrough Breast Cancer Research Unit, said: “This research may show why some women whose cancer has spread to the lymph nodes do not respond to treatment. With an additional test we may be able to treat women more effectively and also make more efficient use of NHS resources.”

A clinical trial needs to be carried out to fully evaluate the benefits of testing cancer cells in the lymph nodes before it can be approved for use on the NHS.

*All Breast Cancer Report, NHS Cancer Screening Programmes, October 2009