There are many things that families share other than their genetic makeup, such as common dietary habits and similar environmental exposures. A family history of breast cancer remains on the National Cancer Institute’s list of risk factors for breast cancer. So what does it mean when cancer “runs in the family?"
“Identification of genes which, when mutated in a family, predispose the carriers to a much higher risk of cancer has been the objective of investigators for decades,” says Bradley A. Arrick, MD, PhD, MHCM, a medical oncologist in the Comprehensive Breast Program and director of the Familial Cancer Program at Dartmouth and Dartmouth-Hitchcock Norris Cotton Cancer Center (NCCC). “Two of the best known genes of this sort are BRCA1 and BRCA2. These two genes provide examples of a number of features we have come to recognize in families and patients in the genetic testing process.”
Inherited mutations in BRCA1 and BRCA2 predispose individuals to more than just one type of cancer. “Even though they were identified by examining families with excessive amounts of breast cancer, affecting women in multiple generations, it was clear early on that these women were also at risk for ovarian cancer,” says Arrick. Other tumor types, such as pancreatic cancer, also can occur at increased frequency in carriers. “There are thousands of possible mutations in BRCA1 and BRCA2 that predispose the carrier to cancer. With current technology, until it is determined which gene mutation is in a specific family, a negative genetic test result in the members of that family cannot be interpreted as ruling out the possibility of a heritable predisposition. In other words, if you don’t know what you’re looking for, not finding it isn’t a conclusive answer,” says Arrick.
Genetic testing has improved greatly in recent years. Since the 1990s, researchers have known about BRCA1 and BRCA2, which are associated with higher risks of breast, ovarian and other cancers. More recently, patients with different forms of cancer who inherited mutations in one of these genes have been found to benefit from a new form of oral anti-cancer treatments, called PARP inhibitors. “These advances have raised the value of genetic testing in more patients than before, even when there is not a strong family history of cancer,” says Arrick.
Today, genetic testing is available for many more genes than just a few years ago, and research has highlighted that a strong family history of cancer is not always a reliable factor for limiting testing to those select few. Also, the cost of testing is about one-tenth of what it was a decade ago. These developments are making genetic evaluation increasingly important to the care of patients with breast and other cancers.
For some cancer patients, genetic testing can also help other members of their family. People who have not had cancer, but who carry the same gene mutations as a family member who does become eligible for more intensive screening tests and preventative measures, which could ultimately save their lives. Genetic counselors have special training to help patients and their families understand these matters and guide appropriate testing.
The Familial Cancer Program at NCCC provides genetic testing and counseling for people who may have an increased risk of cancer because of their personal or family history. Genetic testing and counseling may be appropriate for anyone with several family members who have had cancer, especially multiple cancers or cancer at an unusually young age, as well as rare cancers. Cancer survivors may also benefit from counseling regarding their risk of a second cancer.
The Familial Cancer Program offers genetic counseling either in person in Lebanon and Manchester, or via phone consultation. For many patients, the genetic test can be done on a saliva specimen that is self-collected using a special kit that can be sent to their homes.