Why Bigger Isn't Always Better

Breast cancer and breast size association discovered

(RxWiki News) We're obsessed with size in this country. And when it comes to breasts, size matters - a lot. Yet bigger is not always better in terms of breast cancer risks.

The size of a woman's breasts is at least partly determined by seven genetic links, and three of those links are strongly associated with breast cancer, according to new research.

"Assess your breast cancer risks."

A personal genetics company - 23andMe - conducted what's called a genome-wide association study and identified the seven genetic links known as single-nucleotide polymorphisms (SNPs).

It is the first study of its kind to identify genetic variants relating to breast size.

The company analyzed the data from 16,175 women customers, who were surveyed about their bra size. Researchers factored in age, genetic ancestry, pregnancies, breast feeding history and breast surgeries.

"The findings in this study show that some of the same biological pathways underlie both normal breast growth and breast cancer," said lead author Nicholas Eriksson, PhD.

"Some studies have found that larger breast size as a young woman is associated with a slightly higher risk for breast cancer. The genetic factors we found support this concept that breast size and breast cancer are related," he said.

The genetic factors identified play a role in breast cancer behaviors. One of the SNPs manages the expression of the estrogen receptor gene. Breast cancers that are estrogen receptor-positive (ER+) are fed by estrogen.

Another SNP is found in an area where abnormalities occur in people with a specific subtype of breast cancer.

"Although the connections between these genetic factors, breast size, and breast cancer aren’t fully understood, our findings give clues to the function of some of these genes and regions that might be useful in combating breast cancer," the company writes on its blog.

23andMe is collaborating with pharmaceutical company, Genentech, in its Invite Study to learn how genes affect treatment of metastatic breast cancer.

Review Date: 
July 5, 2012