72 major genetic risk factors for breast cancer identified in new study

by: Fiza Pirani, Atlanta Journal-Constitution Updated:

Two new studies published Monday in the journals Nature and Nature Genetics revealed 72 previously unknown genetic risk factors — or gene mutations — that lead to the development of breast cancer.

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The studies encompass work from more than 500 researchers at 300 institutions around the world, a collaboration headed by the OncoArray Consortium, a global network of scientists studying genomics.

The researchers examined genetic data, including blood samples, from a combined 275,000 women, 146,000 of whom had been diagnosed with breast cancer.

The bulk of the mutations found (65) predispose to the most common type of breast cancer, hormone receptor-positive (or ER-positive) breast cancer.

The other seven predispose to hormone receptor-negative breast cancer.

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“These findings add significantly to our understanding of the inherited basis of breast cancer as well as identifying new genetic variants, we have also confirmed many that we had previously suspected,” study investigator Doug Easton of the University of Cambridge said. “There are some clear patterns in the genetic variants that should help us understand why some women are predisposed to breast cancer, and which genes and mechanisms are involved.”

How much can the newly identified genes predict about breast cancer risk?

Hormone receptor-positive breast cancer

There is sufficient scientific evidence to prove first-degree relatives of a hormone receptor-positive breast cancer patient have double the risk of getting breast cancer themselves compared to women without a family history of the cancer. 

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After studying 122,977 cases of ER-positive cases, researchers can explain an additional 4 percent of that heritable breast cancer risk.

Previous research about the presence of common BRCA1 and BRCA 2 gene mutations show they also account for about 17 percent of heritable breast cancer risk.

With what the medical community already knows about BRCA1, BRCA2, other variants, plus the newly identified genes, it’s estimated that about 39 percent of heritable ER-positive breast cancer risk can be explained, researchers said.

Hormone receptor-negative breast cancer

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While studying 21,468 ER-negative cases, the researchers identified 10 new gene mutations that could explain approximately 1.5 of the heritable risk of ER-negative breast cancer. With the new research and previous research, the researchers can now explain 14 percent of the heritable risk.

“If you can differentiate women into groups of sufficiently different risks, you might be able to save more lives,” Roger Mine, lead researcher of the “Nature Genetics” study and co-author of the “Nature” study, said. One example: Women with different risks could receive tailored screenings. 

Read the full ER-negative study in Nature Genetics.

The researchers encourage clinicians to apply the new findings at the clinical level, but also urge future researchers to further study the mechanisms of the newly-identified gene mutations to learn more about how cancer manifests itself and how it can be better detected.

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