Well + Being
After years of unexplained fainting, a 'tilt table test' pinpointed the cause
By Mikkael Sekeres, MD The Washington Post
Published August 7, 2026
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How much does family history matter when it comes to cancer risk? Am I definitely going to get it if it runs in my family?
The patient sitting a few feet away from me in my examination room was in her late 80s and had just been diagnosed with leukemia. Her son and daughter were sitting by her side. As part of my routine series of questions when I first meet someone, I asked if anyone else in her family had cancer.
"Well, yes," she answered, "my mother had multiple myeloma, in her 60s." I asked if there was anyone else with cancer.
"Me!" Her daughter volunteered. "I had breast cancer, also in my 60s." I dutifully typed the information into her medical record.
"Does that mean cancer runs in our family?" my patient asked.
I've wondered the same thing. As I've written before, my mom has lung cancer, and both her brother and mother were diagnosed with leukemia. On my dad's side of the family, his father had prostate cancer and mother had ovarian cancer. That's five close relatives with cancer.
But does my family history of cancer mean that my own risk of cancer is higher? What about my patient's family?
Before worrying, keep in mind that the majority of cancer cases - about 90 percent - are not due to an inherited gene, but are completely random, arising in whole or in part from lifestyle or other factors. On the plus side, an estimated 40 percent of all cancers are thought to be preventable by exercising, avoiding smoking, limiting alcohol and making other healthy choices.
There are a handful of identified variants of specific genes that are linked to a higher risk of cancer.
Again, only up to 12 percent of all cancers are believed to be associated with inherited genetic mutations, what we colloquially call cancer that runs in the family.
Clues that you may have inherited a proclivity to develop cancer include multiple close family members on the same side of the family who have similar cancers; cancers developing in younger (under age 50) family members - especially cancers of the ovary, pancreas, colon and rectum, metastatic prostate cancer, male breast cancer or "triple-negative" breast cancer; and several different types of cancer that occur in the same person. Any one of these should prompt consideration of genetic testing.
Some of the more common inherited genetic mutations linked to cancer include:
BRCA1 and BRCA2, which are found in families in whom multiple members develop breast, ovarian and prostate cancers, among others. About 1 in 400 people in the general population carry one of these genes, but among people of Ashkenazi Jewish descent, the prevalence is higher, at about 1 in 50.
MLH1, MSH2, MSH6 and PMS2, which can lead to colorectal, gastric, ovarian and endometrial cancers, among others, and are often referred to as Lynch syndrome. The population prevalence of carrying one of these mutations is almost 1 in 300.
TP53, which can lead to a variety of malignancies, including cancers of the breast, bone and soft tissue, brain, adrenal gland and leukemia, among others - collectively referred to as Li-Fraumeni syndrome. Carriers can develop multiple cancers, with women tending to have breast cancer first, and men initially having brain or soft tissue cancers. It is estimated that up to 1 in 5,000 people have inherited a TP53 variant that predisposes them to cancer.
While inherited genetic mutations can lead to cancers in younger adults, it is increasingly being recognized that these cancers can even occur later in life. Cancer is a multistep process, and having one inherited genetic mutation usually isn't enough to cause the cancer. For example, colleagues and I discovered one inherited genetic mutation in identical twins who developed a form of leukemia in their late 60s, suggesting that additional mutations had to arise over the course of their lives for the cancer to occur.
Having a family history of cancer increases your cancer risk, even without a known inherited mutation.
Having a family history of cancer increases your cancer risk, even without a known inherited mutation.
Because of our family history of cancer, my mom underwent genetic testing and - good news - no inherited cancer gene was found. Despite the number of people with cancer on her side of the family, there was no unifying genetic cause. Instead, the cases were random, and she therefore was unlikely to pass on a known cancer gene to me. I still have no idea, though, whether my dad's side of the family could have such a gene.
Similarly, even though my patient's family had quite a few cancer cases, the pattern was not typical of an inherited genetic mutation.
As a general statement, and for a number of cancers, people with a first-degree relative - defined as a parent, sibling or child - with cancer have two to five times the risk (compared with those without a family history) of developing the same cancer. This may be related to some other type of susceptibility - such as having a similar complexion that's more sensitive to UV damage - or to a lifestyle or environmental risk factor in common, such as smoking.
But without an identifiable genetic mutation at play, it's hard to know just how much a family history puts you at risk. Knowing that I am at increased risk for cancer based solely on my family's history of cancer, I have tried to adopt healthy lifestyle choices, such as exercising, eating a balanced diet, and avoiding smoking and excess alcohol intake, to minimize that risk.
Even if you have an inherited genetic mutation, it doesn't mean you will definitely get cancer
People who inherit one of those common cancer genes have a high risk of developing cancer - much higher than the general population. But cancer is not inevitable.
For example, while about 13 percent of women in the general U.S. population can expect to have a breast cancer diagnosis in their lifetimes, 55 to 72 percent of women who inherit the BRCA1 variant and 45 to 69 percent of women who inherit a BRCA2 variant will develop breast cancer by 70 to 80 years of age. Cancer risk for carriers of one of these mutations is unquestionably higher than the general population - but it is not 100 percent.
If you have an inherited genetic mutation, you can lower your cancer risk
For example, in women who have inherited BRCA1 or BRCA2 variants, options to reduce cancer risk include enhanced screening - with annual breast imaging starting at age 25 - or risk-reducing surgery such as preventive mastectomy or ovary removal, which can also be recommended for people with Lynch syndrome. This strategy was famously chosen by the actress Angelina Jolie, who is a BRCA carrier, and her decision led to higher testing rates for BRCA variants and to other women choosing to undergo risk-reducing mastectomy.
Cancer prevention with medications may also help: Oral contraceptive pills, for example, may reduce the risk of ovarian cancer in women with one of these variants by 44 to 61 percent.
For people with Lynch syndrome, colonoscopy screening for cancer should start in a person's 20s, or five years before the youngest age of colorectal cancer diagnosis in an affected family member, and continue every one to two years. The idea is that this is early enough that a nascent cancer can be identified quickly and removed before it becomes more aggressive or spreads. Taking a daily aspirin may also help; one study found that when taken for a minimum of two years, 600 milligrams daily of aspirin reduced the risk of colon cancer by about 60 percent.
Cancer is complicated. The cards we're dealt at birth play an important role, but risk is influenced by many factors that occur over our lifetime. Regardless of your family history of cancer, minimizing or eliminating additional lifestyle risk factors and engaging in cancer screening programs is something you can control.
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Mikkael A. Sekeres, MD, MS, is the chief of the division of hematology and professor of medicine at the Sylvester Comprehensive Cancer Center, University of Miami. He is author of the books "When Blood Breaks Down: Life Lessons From Leukemia" and "Drugs and the FDA: Safety, Efficacy, and the Public's Trust."