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What You Should Know About Hereditary Cancer


May 26, 2008 — In this edition of Siteman Cancer Center’s podcast series, geneticist Alison Whelan, MD, discusses hereditary cancer and why it’s important to examine your family history.


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On this edition of Cancer Connection, we’ll talk about hereditary cancer, what cancers can be passed on and what goes into genetic testing for the disease.

Host: Thanks for downloading this podcast from the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis. I’m Jason Merrill. Hereditary cancer is a cancer risk that’s inherited or passed on in a family. Unlike most cancer, hereditary cancer results from an abnormal alteration in a single gene. To tell us more about hereditary cancer is Allison Whelan. She is co-director of the hereditary cancer core at the Siteman Cancer Center in St. Louis. Dr. Whelan, thank you for joining us.

Whelan: It’s my pleasure, nice to see you.

Host: What is hereditary cancer?

Whelan: So when you think about cancer, it’s very common in the United States, and generally it’s caused by a combination of environmental and genetic effects. Hereditary cancer is a really small subset of cancer that’s due to a single gene that can be passed on through families that causes a very high likelihood of developing cancer, a high predisposition to cancer.

Host: What cancers are hereditary?

Whelan: About 5 to 10 percent of all cancer is hereditary, and the ones that we think about most frequently are hereditary breast and ovarian cancer or hereditary colon cancer. But there’s also some skin cancers, particularly melanoma, some kidney cancers, and a variety of other cancers can also be hereditary.

Host: So someone whose mom had breast cancer or whose dad had colon cancer, who should consider a cancer risk assessment?

Whelan: So when you think about cancer in a family, cancer is so common that most people will have one or two people in their family who’ve had cancer. But because there’s a single gene traveling in the family and what we see as the red flags of hereditary cancer are if a person has had very early age of onset, so about 10 years earlier than you would normally see that kind of cancer in someone. Or if someone has had two different primary cancers, that’s another red flag. And then you look at the whole family. And so the more relatives that are closely related that have had similar cancers, particularly at an early age of onset, the more that raises a concern for hereditary cancer.

Host: What goes into genetic testing for cancer?

Whelan: So when we talk about genetic testing, that is actually looking specifically for a gene change. But before we ever do the gene testing, we do what’s called cancer risk assessment. We talk to individuals, get their medical history, find out if they’ve had cancer and at what age. And then they collect a family history, looking for what kinds of cancers are in the family and the age of onset. And from there, we can often get a sense of whether they even need to be thinking about hereditary cancer or if they should just pursue regular kinds of cancer screening. If there is a high likelihood that this is a hereditary cancer, then we can talk about the gene testing, which is really just a blood test looking at a specific gene that may be causing the increased risk for cancer. We talk about the limitations of that testing and talk about the benefits of it.

The important thing to think about, if someone is identified as being at an increased risk for cancer and because it’s early age of onset, the care for that person and their family is going to be different. Typically we start screening earlier. So if we’re talking about breast cancer, normally you begin mammograms at age 40. If someone’s part of a hereditary breast cancer family or has been found to have one of the breast cancer genes, we begin screening as early as 25, and instead of just doing a mammogram, we do a mammogram and MRI. And then you can consider more significant preventive strategies, such as preventive surgery, as well.

Host: You mentioned genes that you look for in those blood tests. A lot of people who search online about genetic cancer, they see BRCA1 and BRCA2 a lot. What are those genes, and what should women know?

Whelan: So the BRCA1 and BRCA2 genes are the most common genes associated with hereditary breast cancer. There are actually a couple other genes that are much more rare that can be associated with hereditary breast cancer as well. And we think about BRCA testing in women who have multiple family members who have had breast cancer, particularly if it’s early age of onset with or without ovarian cancer as well. And if someone is found to have the BRCA1 or BRCA2 gene mutation, then the early screening that we talked about is recommended or even preventive surgery. So women who have had a single relative – an aunt who had breast cancer in her fifties or even a mom who had breast cancer in her fifties – they don’t need to be thinking about BRCA1 or 2. But if they have a sister who had breast cancer in her thirties, a maternal aunt, a maternal grandmother and then throw in an ovarian cancer, they’re at increased risk for breast cancer, and they should found out what that risk really is and what they should be doing about it.

Host: What are some other hereditary cancer syndromes?

Whelan: So we talked about the breast cancer risk. The second most common is actually hereditary colon cancer, and probably between 5 and 10 percent of all colon cancer is hereditary. Again, the things that we look for are multiple family members with colon cancer, people who have had colon cancer at an early age – we’re talking in their thirties or forties. And then the genes that increase the likelihood for colon cancer also increase the likelihood for uterine or endometrial cancer, so we also look carefully in the family for that as well.

Host: Overall, what’s the message that you want people to know about hereditary cancer?

Whelan: That most cancer is not hereditary and that doing usual screening is the most important thing to do. But everyone should take their family history. And when you get your family history, find out what kind of cancers people had and what age they had it. Talk to your doctor, and if there’s multiple people and they’ve had early age of onset or they’ve had the same kind of cancers, then it may be worth getting more information, finding out what your risk really is. Because you can do something about it, whether it’s early screening or preventive strategies.

Host: Dr Whalen, think you for joining us.

Whelan: Thank you.

Host: For more information about hereditary cancer, you can visit the Siteman Cancer Center online at or call 800-600-3606. Thanks for downloading. Until next time, I’m Jason Merrill.