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Missing link in breast cancer gene mutations

Missing link in breast cancer gene mutations - Featured Image

Whilst genetic testing for breast cancer has become cheaper and more accessible, there still remains a missing link, experts write in the Medical Journal of Australia.

The BRCA1 and BRCA2 gene are responsible for 2% of breast cancers, however the challenge is to find the “missing heritability” responsible for the other 3% believed to be caused by gene mutations.

Many families with a history of breast cancer don’t have a BRCA1 and BRCA2 gene. It’s believed rare mutations in other genes must have a role in breast cancer, particularly when it’s diagnosed at an early age.

Professor Ingrid Winship, Executive Director of Research at Melbourne Health and Professor of Adult Clinical Genetics at the University of Melbourne and Royal Melbourne Hospital, and Professor Melissa Southey, from the Department of Pathology at the University of Melbourne, say that to, date, testing one gene at a time has had a very high cost however things are starting to change.

“The revolution in our capacity to conduct genetic analyses in very recent years has had a profound impact on how genetic testing services can be applied,” they wrote.

“Now, a panel of multiple genes can be screened for mutations in a single test, at considerably reduced cost, via the application of massively parallel sequencing technology.”

Related: MJA – Direct-to-consumer genetic testing — a regulatory nightmare?

This testing has led to the discover of more genes associated with breast cancer susceptibility.

“Genes that are regularly included in breast cancer susceptibility gene panels that are currently available through academic or commercial testing laboratories include BRCA1, BRCA2, PALB2, PTEN, STK11, TP53, ATM, BARD1, BRIP1, CDH1, CHEK2, MRE11A, MUTYH, NBN, NF1, RAD50 and RAD51C.”

The problem with the discovery of these genes is that it identifies variants of unknown significance.

“A large grey zone exists, the so-called variants of uncertain significance, where classification is not possible, and this information cannot be used clinically,” they wrote.

Related: Genetic testing “appropriate”

“For this reason, interpretation of results, whether derived from gene panels or single gene testing, remains highly specialised and requires a team of skilled scientists, informaticians and genetic practitioners, along with research-derived evidence.”

They conclude that the testing can also produce unintended, secondary findings that were not anticipated.

“The consequences — that is, the clinical validity and utility of many of the genes listed — are not yet clear.”

Read the full clinical focus in the Medical Journal of Australia.

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