THURSDAY, October 28, 2010 (HealthDay News) -- Women with female relatives who have had breast or ovarian cancer are often acutely aware of their own increased risk and may seek genetic counseling.
But they should also pay attention to their father's family history, one genetic counselor warns.
The inherited genetic predisposition to breast and ovarian cancer is mostly caused by a mutation in one or both of the BRCA1 or BRCA2 tumor suppressor genes, said Jeanna McCuaig, a genetic counselor at Princess Margaret Hospital in Toronto. And, she pointed out, "if your mom or your dad has a BRCA1 or BRCA2 mutation, you would have a 50 percent chance of inheriting it from either one."
That explains why a father's family history is as important to consider as a mother's, she said.
"Anecdotally, I've had patients come in and say, 'I never thought about my dad's side,'" McCuaig said. She decided to do some research into the implications of that statement. "We took two years of patient charts referred to our clinic, referred as new patients, and looked to see how many had relatives [with breast or ovarian cancers] on the mom's side versus the dad," she said.
She found that patients who came to her Familial Breast and Ovarian Cancer Clinic at the hospital were more than five times more likely to be referred with a maternal family history of breast or ovarian cancer than a paternal history of such cancers.
To get the word out, she wrote a commentary on the subject, published online in The Lancet Oncology.
The lack of awareness that women may inherit a mutated gene from their fathers is also present among many health-care providers, McCuaig suspects. This is problematic, she noted in her study, because they often serve as gatekeepers for referrals to specialized clinics, including those that do genetic testing.
If a woman tests positive for a BRCA1 or BRCA2 mutation, she has about a 50 percent to 85 percent risk of breast cancer in her lifetime, said McCuaig, citing various studies, and about a 20 percent to 44 percent risk of ovarian cancer.
In contrast, the lifetime risk of developing ovarian cancer in the general population is 1.4 percent, according to the National Cancer Institute, which also states that women who inherit a BRCA1 or BRCA2 mutation are about five times as likely to develop breast cancer as women without such a mutation.
Men with the BRCA 2 mutation have a 6 percent risk of breast cancer, McCuaig said, compared to less than 1 percent in the general male population. Men with BRCA1 or BRCA2 mutation also have a higher prostate cancer risk than other men, she said.
According to the study, about 20 percent to 30 percent of the more than 690,000 women diagnosed with breast cancer and nearly 190,000 diagnosed with ovarian cancer in developed countries have a family history of cancer, the study noted, and between 5 percent and 10 percent are due mostly to an inherited mutation in one of the BRCA1 and BRCA2 genes.
Women and men should take into account the cancer history on both their parents' sides of the family, McCuaig said, and health-care providers should ask about both sides when taking a medical history.
"It's an important point," said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society. "For those of us in cancer treatment, it's not new information, but it's very important for patients and family to be aware of this and not forget" to consider the father's history.
"The bottom line? The family history [of breast and ovarian cancer] in the women in your father's family is every bit as important as the family history of the women on your mother's side," he said.
To learn about BRCA1 and BRCA2 mutations, visit the U.S. National Cancer Institute.