Breast cancers change when they spread

[Posted: Wed 04/11/2009 by Olivia Fens]

One in three breast cancers change form when they spread, a new study has found.

Researchers from the Breakthrough Breast Cancer Research Unit at the University of Edinburgh said this could be why some women whose cancer has spread do not respond to treatment.

Breast cancer is a complex disease, with many different types, which can be treated in different ways.

In the study, the researchers analysed 211 tumours, which had spread from the breast to the lymph nodes in the armpit – the place where breast cancer usually spreads to first.

In 39% of cases the disease in the lymph nodes had changed type.

The researchers said they 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 would mean hormone therapies such as tamoxifen, which would not have worked for the original tumour but 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 that would not work.

“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,” the researchers said.

The study was published in the journal Annals of Oncology.