The Family Cancer Tree
Accurate reporting of family histories could be key to risk reduction.
By Mitzi Baker
Sue Friedman never knew her father's mother, who died of some type of abdominal cancer long before she was born. Yet there's a good chance that her own diagnosis of stage II breast cancer at age 34 was the result of a genetic mutation that was lurking in that branch of her family tree.
In 1997, shortly before she was diagnosed with invasive cancer, the veterinarian from Coral Springs, Fla., read a magazine article in a doctor’s office about a simple blood test that could identify inherited mutations in the BRCA1 and BRCA2 genes. People with these mutations face increased risk of developing breast and ovarian cancer. Friedman learned that women of Ashkenazi (Eastern European) Jewish descent, like herself, are more likely to carry BRCA mutations, and she quickly realized how little she knew about her young grandmother’s illness.
After her own diagnosis, Friedman sought genetic counseling and then a blood test for the mutations. In February 1998, she received the news: She had a BRCA2 mutation. Friedman began to suspect that her paternal grandmother may have had ovarian cancer. “My dad talked about his mother all the time,” says Friedman, who in 1999 founded Facing Our Risk of Cancer Empowered (FORCE), a nonprofit organization that focuses on getting the word out about hereditary breast and ovarian cancer. “But other than [his] telling me that she died young of cancer, and that the doctors couldn't do much for her once it was discovered, her illness and death were not mentioned.”
“The presence of cancer in one's close relatives may influence one's own health care.”
Like Friedman, many people don’t know their family history of cancer. As recent studies have shown, a person’s knowledge of family members’ health is frequently imprecise or even flat-out wrong. But taking steps to uncover these hidden clues to cancer risk may pay off: Even when a person doesn’t have a known inherited cancer mutation, knowledge of family cancer history can inform decisions about cancer screening. A family history may also play a role in whether a patient seeks genetic testing or learns about a risk of developing additional cancers. Such information may even influence treatment choices for some patients, Friedman suggests.
The Value of an Accurate History
Only about 5 to 10 percent of all cancers are the result of inherited genetic mutations, and most cancers occur in people with little or no family history of the disease. But nearly one in four people are estimated to have a family history that suggests a predisposition to cancer, according to a study published in the journal Genetics in Medicine in November 2010.
Identifying those individuals who have a family history of a specific cancer is important, says Phuong Mai, a medical oncologist with the National Cancer Institute (NCI) who was not involved with that study, “because the presence of cancer in relatives might suggest that the individual’s risk for that same cancer is increased.”
And that’s knowledge on which many individuals may be able to act to reduce their risk.
Having a family history of cancer converts basic cancer screening into cancer surveillance, explains Margaret Eberl, a family practice and preventive medicine physician in Buffalo, N.Y. Knowledge of one’s family history may change not only at what age cancer screening should begin, but also how frequently the screening occurs.
People with a strong family history of colorectal cancer, for example, should undergo screening with colonoscopy every five years, beginning at 40 or 10 years less than the age of the youngest person diagnosed in the family, according to the American Cancer Society (ACS). During a colonoscopy, polyps can be found and removed, including those that may be precancerous. For individuals not at high risk, guidelines recommend colonoscopy every 10 years beginning at age 50, or use of an alternate screening method. (See “Getting Screened.”
For breast cancer, the ACS recommends that women at high risk—including those who have a BRCA mutation or a first-degree relative with a BRCA mutation—begin to receive annual screening by mammography and MRI by age 30, which is 10 to 20 years earlier than the guidelines that cancer organizations recommend for women at average risk. Screening may detect breast cancer early; however, only limited evidence supports the age at which to begin screening, so patients are advised to discuss personal circumstances with their health care providers to determine the best course of action.
Beyond screening, says Eberl, “rapidly accumulating evidence” is showing that lifestyle interventions—such as maintaining a healthy body weight, getting more exercise, quitting smoking and limiting alcohol consumption—may contribute to lower risk of cancer for someone with a family history.
Some cancer patients with a strong family history of cancer may have an inherited cancer syndrome that can be identified through genetic testing. (See “Hereditary Cancer Syndromes.”
) For patients with one of these syndromes, there may be an increased risk of developing a second cancer, either of the same type or a related one, according to Mai.
Knowing about her increased cancer risk was especially important to Friedman: Her inherited BRCA2 mutation meant that she has hereditary breast and ovarian cancer syndrome. It put her at extremely high risk of developing a second breast cancer and ovarian cancer—which often goes undetected and undiagnosed until it has advanced to a late stage. She decided to reduce her risk by having surgery to remove her noncancerous breast as well as her ovaries and uterus.
Friedman had most likely inherited her risk-raising BRCA2 mutation from her grandmother, who passed it on to her father, who then passed it on to her. So she began alerting her family members—including cousins she hadn't spoken with in more than 20 years—about their potential risks, as well. The conversations were not easy, but Friedman believed it was her obligation to inform. “There are still many people who do not understand hereditary cancer or the risks,” she says.