According to study results released this Monday, women with a close relative with breast cancer may not be at a higher risk of getting breast cancer. The findings may bring comfort to women from high-risk families after a 2007 study suggested that simply having a relative with a BRCA1 or BRCA2 mutation raised their risk of developing breast cancer, even if they had tested negative for the genes.
“The results are encouraging and reassuring,” said Dr. Allison Kurian of Stanford University School of Medicine, whose study appears in the Journal of Clinical Oncology.
The average woman in the United States has about a 12 to 13 percent chance of developing breast cancer in her lifetime. Some 5 percent to 10 percent of breast cancers are genetic, and most of these cases are caused by abnormalities in the BRCA1 or BRCA2 genes. Women with these mutations have a five to twenty times higher risk of developing breast or ovarian cancer, and must undergo intensive cancer screenings and take other precautions to reduce their cancer risk. Many of these women elect to have their breasts or ovaries removed to keep from developing cancer.
Once these mutations turn up in a family, other family members are screened as well. Women from these families who test negative have traditionally been told they have about the same risk as women in the general population. However a 2007 study published in the Journal of Medical Genetics challenged that notion, suggesting that even though women did not carry the family breast cancer mutation, they still had a two to five times higher risk of developing breast cancer.
To study this, Kurian and her team analyzed data on more than 3,000 families with BRCA1 or BRCA2 mutations from three countries: the United States, Canada and Australia. They compared breast cancer rates among carriers and non-carriers of family mutations of the BRCA1 and BRCA2 genes. They found no evidence of an increased breast cancer risk among women who were non-carriers. “It's reassuring that we don't see a signal for elevated breast cancer risk from women who test negative for a familial mutation,” Kurian said.
“This isn't to say that women may not have other reasons for increased risk due to other factors,” said Kurian. “Cases should be managed in an individual way.”
Breast cancer is the most common cancer among women in the United States. More than one in eight women will develop the disease in their lifetimes, according to Breastcancer.org.
“I am really happy to see a relatively large, well done study begin to put an end to this controversy,” said Dr. David Euhus, professor of surgical oncology at University of Texas Southwestern Medical Center. “These results make sense. Women from BRCA families who did not inherit the mutation can still get breast cancer, but their risk is no where near as high as their relatives who did inherit the mutation.”
“Women with a family history of breast cancer are understandably worried about their own risk of developing breast cancer,” Dr. Harold Burstein, breast oncologist at Dana-Farber Institute at Boston, said. “This study provides strong reassurance that 'no means no' when it comes to negative results on the BRCA1 / BRCA2 genetic tests for these patients. That is, despite the family history, the risk of breast cancer is not greater than that for ordinary women in similar circumstances when the genetic test is 'normal,'” he added.
Genetic testing is stressful for many patients, said Dr. Hope Rugo, director of breast oncology and clinical trials education at UCSF. It's critical that once patients undergo testing, they're able to feel confident about what the results mean - whether they're positive for a BRCA mutation and need more follow-up, or they're negative and can trust that their risk of developing cancer is still relatively low. While Rugo wasn't surprised by the results of the Stanford study, she said she appreciates the reassurance it provides. “It's important to remember that women have a relatively small risk of inheriting the same gene” as a family member with the mutation, Rugo said. “If they did inherit it, there are things they can do to protect themselves. And if they didn't, they're free. They fall back into the general population.”
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