How You Can Inherit Cancer From Your Parents

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Last year, a man in his early 70’s was diagnosed with pancreatic cancer. His two daughters didn’t realize how his diagnosis affected their own health, but when a genetic test to determine how his cancer might respond to a new treatment revealed a BRCA2 mutation, his children turned to genetic testing for answers.

They discovered they each had the same mutation, putting them at increased risk of developing pancreatic, breast and ovarian cancer. This knowledge allowed them to make informed decisions about their preventive treatment and care – decisions that may have saved their lives.

Yes, You Can Inherit Risk For Breast Cancer From Your Dad

“My mom didn’t have breast cancer and neither did my grandmother, so I’m really not at risk.” Genetic counselors specializing in cancer risk across the U.S. have heard countless iterations of this particular statement, and most patients are shocked to learn that hereditary cancer is genderless. A cisgender female can inherit an increased risk of developing breast cancer from their father, and a cisgender male can inherit an increased risk of developing prostate cancer from their mother, and vice versa. How is that possible?

We inherit half of our DNA from each biological parent. Therefore, we are just as likely to inherit certain traits and/or risks for disease from our biological mother’s side as we are from our biological father’s side.

As a cancer genetic counselor, I assess family histories to help make a more accurate risk assessment for an individual. To do this, I ask specific questions about family structure, types of cancer relatives have been diagnosed with, and at what ages they first presented with a cancer diagnosis. Some clues that could point to a hereditary cancer syndrome in a family include, but are not limited to:

  • Cancer diagnosed at early ages; under the age of 50 is typically referred to as an earlier age of diagnosis
  • Multiple family members with cancer on the same side of the family
  • Family members with cancer in multiple generations on the same side of the family
  • Certain types of cancer, such as ovarian or pancreatic
  • Certain patterns of cancer within a family such as breast/ovarian/prostate or uterine/colorectal cancer

Even if someone reports a strong family history of colon cancer on their mother’s side and that is what they are most concerned about, it is important to collect information regarding cancer history on the individual’s father’s side as well. While rare, some individuals can be at risk for a hereditary cancer syndrome coming from both their maternal AND their paternal side!

The Odds Of Hereditary Cancer

Consider this example: Your paternal grandmother (father’s mother) was diagnosed with ovarian cancer at age 70. Genetic testing reveals she has a BRCA1 pathogenic variant, also commonly called a BRCA1 gene mutation. Women with a BRCA1 mutation have increased risks of developing breast, ovarian and pancreatic cancer in their lifetime, and possibly an increased risk for melanoma. Men with a BRCA1 mutation have increased risks of developing male breast, prostate, and pancreatic cancer in their lifetime, as well as possibly melanoma. Each biological child of your paternal grandmother has a 50 percent chance of having inherited this BRCA1 mutation, and being at increased risk to develop cancer. This means that, even though your father has never had a cancer diagnosis, he has a 50 percent chance of carrying this same BRCA1 mutation.

Even though men have an increased risk of developing cancer with a BRCA1 mutation, their risks are different from women with a BRCA1 mutation. Male breast cancer is still uncommon even with a BRCA1 mutation. While the risk for prostate cancer is significantly increased for men who carry a BRCA1 mutation, many still do not show any sign of it – meaning that they most likely will not be diagnosed with a cancer. Essentially, it can be harder to “see evidence of” certain hereditary cancer gene mutations even when they are present on the paternal side.

Let’s say your father did inherit the BRCA1 mutation from his mother. That would then mean that you have a 50 percent chance of having inherited the same BRCA1 mutation from your father. There are guidelines from the National Comprehensive Cancer Network (NCCN®) on how to care for individuals with a BRCA1 mutation, and there are recommendations for screening and preventive surgeries to consider. If you are female, earlier and more frequent breast screenings are recommended, as well as consideration of preventive surgery in relation to breasts and ovaries/fallopian tubes (Angelina Jolie went this route). If you are male, breast screening would be recommended as well as prostate cancer screening, which typically would occur earlier and possibly be more frequent, compared to the general population. Additionally, if you are of reproductive age, whether male or female, this information could impact family planning.

Since we inherit 50 percent of our DNA from each side of our family, a family history of breast cancer, particularly if diagnosed younger than age 50, and/or ovarian cancer on either side of the family is equally relevant to your health. If there is a gene mutation associated with increased cancer risk on your father’s side, you are just as likely to inherit this mutation as you would be if it were on your mother’s side of the family.

Knowing Your Family History Can Save Your Life

Collecting family health history can be difficult; some family members may not feel comfortable sharing their personal health information. Other barriers can also exist, such as:

  • if a relative was adopted (example: mother was adopted so no information may be available for her biological parents/siblings)
  • access to care/screening; relatives may not have insurance and so may not seek medical care
  • relatives living in another country with different screening ages/recommendations

So how can you best prepare for a genetic counseling session? Learn how to talk with relatives and gather important information here.

Preventive Care is the First Step

If you are concerned about your family history of cancer and what your risks may look like, the best first step is to talk with a cancer genetic counselor. They will ask if you know what types of cancer family members have had, the approximate age at which they were diagnosed, and if relevant, what kind of treatment they underwent (i.e. a mastectomy after a breast cancer diagnosis). Sharing this information with a genetic counselor can help them assess your risk for developing cancer and identify potential hereditary cancer syndromes/gene mutations that may be contributing to cancer risk in your family.

If you decide to proceed with cancer genetic testing, then either a blood or saliva sample will be collected, and typically results are available in two to three weeks. Your results may be accompanied by an appointment with your genetic counselor to interpret the findings and explain how the test results impact you/your family. The genetic counselor will also review your risks of developing cancer over your lifetime: whether due to a gene mutation found on testing, or due to your reported family history of cancer.

Recommendations for screening based on age can be made to help you and your healthcare providers prevent cancer as much as possible or catch it as early as possible.

This is exactly the path taken by the daughters of the man diagnosed with pancreatic cancer mentioned at the beginning of this article. When his testing revealed a BRCA2 mutation, they scheduled their own genetic counseling appointments and upon learning about their BRCA2+ status, they took action to help reduce their cancer risks for themselves and their family members.

About the Authors
Ashley Daley, MS, CGC, Director Cancer Genetics
Sheryl Walker, MS, CGC, Specialty Genetic Counselor, Cancer