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Nearly 40 percent of American men and women will be diagnosed with cancer in their lifetimes, and approximately five to 10 percent of these cancers are the result of inherited gene mutations, according to the National Cancer Institute. So, is cancer a genetic disease?

Cancer Prevalence and Heritable Cancer

If cancer runs in your family, it does not necessarily mean that it is heritable cancer — people can also inherit a genetic predisposition to cancer risk factors. If that’s the case, a cancer may be prevalent in your family and yet is not caused by a heritable genetic mutation. This prevalence could occur as a result of lifestyle choices, such as diet or environmental factors, the National Cancer Institute notes.

Harvard Medical School explains the signs of heritable cancer, which include having several relatives or generations of relatives with the same cancer. A first-degree relative with cancer, like a parent or sibling, means a higher probability of cancer than a grandparent, aunt or uncle with cancer.

The American Cancer Society (ACS) suggests creating a list of family members who have had cancer and gathering information about each case, such as age of diagnosis, type of cancer and risk factors. The ACS provides a list of questions that people can use at the outset to learn more about the possibility of genetic cancer. Additionally, it provides a list of characteristics of those who should review their information with a healthcare professional with an expertise in genetics, like a genetic counselor, and consider genetic testing.

Cancer and Genetic Predisposition

Is cancer a genetic disease? Families can share genetic mutations that predispose them to specific cancers, collectively known as family cancer syndrome. There is a 50 percent probability that parents with a hereditary cancer mutation will pass this onto their children.

Perhaps the most common and well-known of these is hereditary breast and ovarian cancer (HBOC) syndrome caused by mutations mostly in the BRCA1 genes, as well as the BRCA2 genes. These mutations increase the risk for cancers of the breast, ovaries, prostate and pancreas.

Another example is Lynch Syndrome, caused by a mutation in mismatch repair genes, or genes that repair damaged DNA. The syndrome increases a person’s genetic predisposition to colon cancer and endometrial cancer, along with cancers of the ovary, stomach, small intestine, pancreas, kidney and brain, according to the ACS.

While these are some of the most prevalent family cancer syndromes, the National Cancer Institute says that more than 50 hereditary cancer syndromes are attributed to gene mutations.

The Difference in Sexes

Some hereditary cancers have different cancer risks for men versus women. With HBOC, for example, the lifetime risk for breast cancer is up to 85 percent, whereas male breast cancer is up to a 6 percent risk. Additionally, men have up to a 20 percent risk for prostate cancer, and women have up to a 50 percent risk for ovarian cancer.

How to Reduce Heritable Cancer Risks

Couples who discover heritable cancer in one or both of their families can help prevent passing on cancer genes to their children through preimplantation genetic testing. PGT for single gene disorders reduces the risk of passing along hereditary cancers and has successfully been used to identify Lynch Syndrome and HBOC, among others. If you have a hereditary genetic mutation and are thinking about starting a family, you may want to consider PGT.