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Nearly a third of cancer cases linked to inherited genes: study

Nearly a third of cancer cases linked to inherited genes: study - Featured Image

A large twin study has found that in some families, there is a shared increased risk of any type of cancer.

Led by researchers  at the Harvard T.H. Chan School of Public Health, the University of Southern Denmark, and the University of Helsinki, the study is the first to look at family risk estimates of common and rarer cancers.

The study, published in JAMA, looked at 23 different types of cancer and familial risk was seen for almost all cancers.

Co-lead author of the study Lorelei Mucci, associate professor of epidemiology at Harvard Chan School said: “Prior studies had provided familial risk and heritability estimates for the common cancers—breast, prostate, and colon—but, for rarer cancers, the studies were too small, or the follow-up time too short, to be able to pinpoint either heritability or family risk.”

Related: MJA – The impact of genomics on the future of medicine and health

Investigators looked at more than 200,000 identical and fraternal twins in Denmark, Finland, Norway, and Sweden, who were part of the Nordic Twin Study of Cancer. The twins were followed over an average of 32 years between 1943 and 2010.

One in three developed cancer in their lifetimes. Cancer was diagnosed in both twins for 3,316 pairs, 38% of identical twins had the same cancer compared to 25% of fraternal twins.

The researchers found that when one twin had been diagnosed with cancer, the fraternal twin’s risk of developing any cancer was 37%. Among identical twins, the risk jumped to 46%.

As fraternal twins are similarly genetically to other non-twin siblings, the study found that there is an increased cancer risk for families when one sibling contracts cancer.

Related: MJA – Preventing breast and ovarian cancers in high-risk BRCA1 and BRCA2 mutation carriers

Overall, the heritability of cancer was estimated at 33%. The cancers with the highest heritability were: skin melanoma (58%), prostate cancer (57%), non-melanoma skin cancer (43%), ovarian cancer (39%), kidney cancer (38%), breast cancer (31%), and uterine cancer (27%).

Co-author Jacob Hjelmborg, from the University of Southern Denmark said: “Because of this study’s size and long follow-up, we can now see key genetic effects for many cancers.

“Findings from this prospective study may be helpful in patient education and cancer risk counselling.”

Read the full study in JAMA.

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