Study Finds Genes Determine One-Third of Cancer Risk

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One-third of our cancer risk is in our genes, new research shows.

A large study of twins found that the heritability of cancer overall is 33 percent — and the heritability of specific cancers is as high as 58 percent.

Heritability is a measure of how much of the variation in a population’s cancer risk is due to genetic factors, according to the Harvard T.H. Chan School of Public Health.

The study was headed by researchers from the Harvard Chan School, the University of Southern Denmark and the University of Helsinki. It was published online Tuesday by the Journal of the American Medical Association and appears in the current print issue of JAMA.

The specific cancer types for which the study found significant heritability include:

  • Skin melanoma (58 percent)
  • Prostate (57 percent)
  • Nonmelanoma skin (43 percent)
  • Ovarian (39 percent)
  • Kidney (38 percent)
  • Breast (31 percent)
  • Uterine (27 percent)

The researchers also looked at the familial risk of cancer, which the Harvard Chan School describes as a measure of the cancer risk in an individual.

They noted a significant familial risk for cancer overall and for specific cancers, including prostate, melanoma, breast, ovarian and uterine.

Lorelei Mucci, associate professor of epidemiology at the Harvard Chan School and co-lead author of the study, explains:

“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.”

This study involved data on more than 80,000 identical and more than 123,000 fraternal twin individuals in Scandinavia who were followed for an average of 32 years between 1943 and 2010.

Overall, 1 in 3 people studied developed cancer over the course of a lifetime.

Co-lead author Jacob Hjelmborg of the University of Southern Denmark explains:

“Because of this study’s size and long follow-up, we can now see key genetic effects for many cancers.”

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