Universiteit Leiden

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Breast cancer risk more accurate after genetic test

Leiden University Medical Center (LUMC) has spent the past five years coordinating an international study of genetic mutations and breast cancer risks. The results will make it easier to determine which genes increase the risk of breast cancer and to what extent. The researchers published their results in the New England Journal of Medicine.

Peter Devilee, Professor of Genetics of Cancer at the LUMC.
Peter Devilee, Professor of Genetics of Cancer at the LUMC.

‘Women around the world who think they may have a higher risk of developing breast cancer, for example because of a family history, can be tested to see if they carry a genetic mutation,’ explains Peter Devilee, Professor of Genetics of Cancer. This is done in diagnostic laboratories with what is known as a multigene panel test, which determines whether several breast cancer genes contain a genetic mutation.

Uncertainty about breast cancer risk

‘Women in the Netherlands can be tested for five breast cancer genes. These obviously include the familiar BRCA1 and BRCA2 genes, but more recently PALB2, CHEK2 and ATM too,’ Devilee explains. ‘For these genes we have a fairly good idea of the breast cancer risk, but this still isn’t very accurate. With the latter three genes, it is particularly difficult to interpret the test in terms of the exact level of the risk of breast cancer.’
It is known that other genes may also influence the risk of breast cancer. ‘The aim of our research was to estimate more accurately the risks relating to the five known breast cancer genes and to research whether other genes –and if so which ones – also increase the risk so that we can possibly expand the test.’

Accurate estimate

All the university medical centres in the Netherlands took part in this study as did the Antoni van Leeuwenhoek hospital. This was through the ‘Hebon’ research network. The international partners in the study tested 34 potential breast cancer genes in more than 60,000 breast cancer patients and 53,000 healthy women.

The results confirm that the five genes that are tested in the Netherlands are at present the most important breast cancer genes. The researchers were also able to provide a more-accurate estimate of the associated breast cancer risk, which will enable clinical geneticists to give clearer advice on the risks. The results also showed that 19 genes are not involved in breast cancer, and that although it was clear that seven other genes can increase the risk of breast cancer, this is nonetheless quite rare.

Greater clarity

The results therefore support current Dutch policy to provide women with results for the five known genes. Clinical geneticists will include the new information in their advice more or less immediately. They will be able to use the more-accurate risk estimates to tailor each test result to the individual woman. ‘The results also provide evidence for the potential expansion of the test,’ says Devilee. ‘In short, thanks to this study women around the world who undergo a multigene panel test will have a much better idea of where they stand.’

Read the full article: Breast Cancer Risk Genes — Association Analysis in More than 113,000 Women.

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