Some breast cancers depend on hormones and some do not. That there exists a biological distinction between the types of breast cancer is reported in the open-access journal PLoS Genetics.

It has been generally accepted in the medical community that hormone dependent breast cancers (ER positive) came from the same biological pathway as breast cancer that are hormone independent (ER negative). The hormone dependent variety is often treated with surgery and anti-hormone drugs, whereas the hormone independent type is treated with surgery and chemotherapy. An international group of cancer researchers, in the largest study of its kind, analyzed over 23,000 cases of breast cancer to further investigate the differences between these two types of breast cancer.

Lead author Dr. Paul Pharoah (University of Cambridge) said: “We looked at five genetic variants associated with breast cancer to see if they were more likely to be found in hormone dependent or independent breast cancers. One common genetic variant, FGFR2, was strongly associated with hormone dependent breast cancer, but weakly associated with hormone independent cancer. This shows that they have distinct genetic origins, and are different diseases.”

“Scientists were previously unsure how different types of breast cancer developed. Although the findings won’t have any immediate effects on the treatment of women with the disease, they are important in helping to define the next steps in our research on the causes of this major cancer,” said Dr Lesley Walker, director of cancer information at Cancer Research UK.

The authors maintain that this new discovery that the cancer types come from separate biological pathways may improve the research efforts in preventing and treating both types of cancer.

Heterogeneity of Breast Cancer Associations with Five Susceptibility Loci by Clinical and Pathological Characteristics
Garcia-Closas M, Hall P, Nevanlinna H, Pooley K, Morrison J, et al.
PLoS Genetics (2008). 4(4):e1000054.
doi:10.1371/journal.pgen.1000054
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Written by: Peter M Crosta