Story highlights
Jimmy Carter's brother, father and two sisters all died from pancreatic cancer
If you've noticed cases of cancer in your family, speak with a genetic counselor
Only about 5% to 10% of all cancers result directly from inherited genes
One look at President Jimmy Carter’s family history, and you have to wonder whether he and his relatives live in fear.
His brother, father and two sisters all died from pancreatic cancer. His mother had breast cancer that later moved to her pancreas. Now Carter, 90, has melanoma that has been found in his liver and brain. The exact cause of the cancer isn’t clear; some 98% of melanomas start with the skin.
But Carter’s pedigree certainly raises suspicion of a sinister gene passed from generation to generation.
Genetic counselors say one thing is for sure: Many families are cursed with cancer, and it can be absolutely terrifying.
“Many of them think it’s not a matter of if they get cancer, but when,” said Joy Larsen Haidle, president of the National Society of Genetic Counselors.
But just because family members had cancer doesn’t necessarily mean you’ll get cancer. There are many variables: Who in your family has had cancer – close or distant relatives? Were they from one side of the family or both? Did they get cancer at a young age, when cancer is rare, or at an older age, when cancer is more common?
If you’ve noticed cases of cancer in your family, the first thing to do is speak with a genetic counselor. Certain family history patterns signal there might be a bad gene in the family, while other patterns might point to a fluke.
If it does turn out you have a serious family history of cancer, the next step is to decide whether you want to go searching for a bad gene. In some cases, as with breast cancer, knowing you have a bad gene can help you make decisions, such as whether to have a mastectomy before cancer strikes. Other times, knowing won’t help you; it may not be worth looking for it.
Whatever you do, Otis Brawley, the chief medical officer at the American Cancer Society, has one piece of advice: Talk to a genetic counselor before you go searching for bad genes, even if it costs a few hundred dollars. Genetics is a tricky, complicated business, and doctors typically don’t know all the ins and outs.
According to the American Cancer Society, only about 5% to 10% of all cancers result directly from inherited bad genes.
“I’ve seen many people waste thousands of dollars,” Brawley said, and some who’ve been given inappropriate testing.
The National Society of Genetic Counselors website has a tool that can help find a genetic counselor near you.
Below is a list of the six cancers in the United States that kill the most people. Together, they take hundreds of thousands of lives every year. Experts shared who should get tested, what that testing means and what you can do with the results.
But first, a few notes:
1. Not all experts agree on what constitutes a family history of cancer. Bottom line: If you’re worried, go talk to a genetic counselor.
2. To constitute a family history, the cancers don’t have to be of the same type – breast, liver, lung etc. Some genes increase the risk of more than one type of cancer, so pay attention to a family history of a variety of cancers, as those cancers might be genetically linked.
3. If testing does not find a bad gene (technically called a gene mutation), that doesn’t mean your family doesn’t have one. It may mean you have a gene mutation that hasn’t been discovered yet, so there isn’t a test for it.
DEADLIEST CANCERS: LUNG
What constitutes a family history of lung cancer?
Research on lung cancer genetics is still in its early stages, so it’s not clear what constitutes a family history. Seek genetic counseling if you have two or more relatives on the same side of the family with lung cancer.
If I have one of these gene mutations, what are the chances I’ll get lung cancer?
About 20 genes are linked to lung cancer, and the risk they confer varies. For example, if you carry a mutation in the p53 gene and you smoke, you have a 50% risk of getting lung cancer in your lifetime, compared to about a 14% risk for smokers who don’t carry a mutation.
Because the research is still in the early stage, consider going to a center that specializes in lung cancer genetics, such as Johns Hopkins in Baltimore, Sloan Kettering in New York, Dartmouth in New Hampshire, the University of Cincinnati or Louisiana State University.
If I do test positive for a gene mutation, what can I do?
First of all, don’t smoke. Second, ask your doctor about screening with a spiral CT scan, which can catch lung cancer at a very early stage. Such screening needs to be considered carefully, since the scan itself contains radiation, which increases the risk of cancer.
To learn more, see information from the Centers for Disease Control and the American Cancer Society.
DEADLIEST CANCERS: COLON
What constitutes a family history of colon cancer?
• If you have two relatives with colon cancer on the same side of your family.
• If you have one relative with early onset colon cancer (age 50 and under).
• If you have a relative who’s had 10 or more benign polyps.
• If a relative has had both colon and endometrial cancer.
• If you’ve been diagnosed with colon cancer at age 50 and under.
If I have one of these gene mutations, what are the chances I’ll get cancer?
Most people have about a 5% to 6% chance of getting colon cancer in their lifetime. People with MLH1 and MSH2, two of the more common mutations for colon cancer, have a 50% to 60% lifetime chance of getting colon cancer. Some 18 other genes are linked to colon cancer, conferring varying levels of risk.
If I do test positive for the gene mutation, what can I do?
You can get regular colonoscopies with a gastroenterologist who has expertise in your genetic mutation.
To learn more, see information from the American Cancer Society.
DEADLIEST CANCERS: BREAST
What constitutes a family history of breast cancer?
• If you have two relatives on the same side of the family with early onset breast or ovarian cancer (early onset means age 50 or younger).
• If you yourself have been diagnosed with breast cancer under age 45 or ovarian cancer at any age; genetic testing can help you make treatment decisions and can help other family members.
• If anyone in your family had triple negative breast cancer under the age of 60.
• If any male relative had breast cancer.
• If you’re of Ashkenazi Jewish heritage and breast or ovarian cancer runs in your family.
If I have one of these gene mutations, what’s the chance I’ll get cancer?
Any woman has about a 12% chance of getting breast cancer. A woman with a BRCA1 mutation may have as high as an 80% risk during her lifetime of getting breast cancer. A woman with a BRCA2 mutation has about a 45% risk. There are about 18 other gene mutations linked to breast cancer, and each one confers a different risk.
If I do test positive for the gene mutation, what can I do?
You can do regular screenings with MRI in addition to mammograms. You can also consider having your breasts and ovaries removed as a preventive measure. (Breast and ovarian cancers are genetically linked.) You can also consider taking the drug tamoxifen.
To learn more, see information from the Susan G. Komen Foundation and the National Society of Genetic Counselors.
DEADLIEST CANCERS: PANCREATIC
What constitutes a family history of pancreatic cancer?
Genetic testing should be considered if two or more close relatives – your parents, siblings or children – have had pancreatic cancer, or if you have a family history of breast, ovarian, or colon cancer or melanoma as well as pancreatic cancer among your close relatives.
If I have one of these genes, what are the chances I’ll get cancer?
There are about 12 gene mutations linked to pancreatic cancer. Depending upon which you have, you have a three- to tenfold increased chance of getting pancreatic cancer compared with someone who doesn’t have a mutation.
If I do test positive for the gene mutation, what can I do?
You may want to become involved in a clinical trial, such as one at Johns Hopkins, the Cancer of the Pancreas Screening-5 CAPS5)Study, where early detection screening is provided by endoscopic ultrasound.
To learn more, see information from the Sol Goldman Pancreatic Cancer Research Center and the American Cancer Society.
DEADLIEST CANCERS: PROSTATE
What constitutes a family history of prostate cancer?
• If you have two or more relatives on the same side with early onset prostate cancer (under age 50).
• If you have any relative with a Gleason score of 7 or higher.
If I have one of these gene mutations, what are the chances I’ll get cancer?
There are about seven gene mutations linked to prostate cancer, and the risk they confer varies. For example, having the BRCA gene mutation means you have about a 20% chance of getting prostate cancer before you turn 70, while men without any mutation have about a 14% chance of getting prostate cancer before turning 70.
If I do test positive for the gene mutation, what can I do?
You can start screening earlier than normal – at age 40, or 10 years before the earliest prostate cancer diagnosis among your relatives, whichever is earlier. For example, if your relative was diagnosed at age 40, start screening at 30. If he was diagnosed at 60, start screening at 40. Doctors will watch your prostate-specific antigen, or PSA, level and how quickly it increases over time.
To learn more, see information from the American Cancer Society and the National Cancer Institute.
DEADLIEST CANCERS: LIVER
It’s not clear whether liver cancer runs in families, and there are no specific genetic tests. If cancer is found in the liver, be sure to ask the doctor whether it started there – many people think they have liver cancer when the cancer actually started somewhere else and spread to the liver.
To learn more, see information from the American Cancer Society.
Sources: The information for breast, liver, prostate and colon cancers came from Larsen Haidle of the National Society of Genetic Counselors and Jason Flanagan, a genetic counselor at Sanford Health in Sioux Falls, South Dakota. Information for pancreatic cancer came from Alison Klein, a geneticist at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins. Information for lung cancer came from Christopher Amos, a geneticist at Dartmouth-Hitchcock Norris Cotton Cancer Center.
CNN Health’s John Bonifield contributed to this story.
