Presented by: Kerry Kingham, MS, CGC
Genetic Counselor, Cancer Genetics Clinic
Stanford Center for Clinical Informatics
September 30, 2009
Although most cancers are not “inherited,” some families are particularly susceptible to cancer and may benefit from early detection or other risk reduction strategies.
- The most common inherited cancers include breast, ovarian, and certain kinds of colorectal cancer.
- A BRCA mutation is linked to a higher risk of developing breast cancer and ovarian cancer, and a higher risk for male breast cancer.
- Genetic tests can help patients understand their risk of develop cancer and allow them to make educated decisions about screening and preventive measures
Hereditary cancer is the development of cancer due to an inherited gene mutation that has been passed from parent to child. People who have inherited a gene mutation have also inherited an increased risk to develop cancer that is higher than those in the general population.
Inherited cancers begin in the DNA, the body’s cellular blueprint. Each cell contains two sets of chromosomes—one from the father and one from the mother—that replicate each time a cell divides. Genes are segments of DNA carried on the chromosomes that determine specific characteristics. Though the body makes proteins to control mutations before cell division, when certain mutations are part of the original programming, they can lead to cancer.
Although most cancers are not “inherited,” some families are susceptible to cancer and may benefit from early detection or other risk reduction strategies. Specialists in the Stanford Cancer Genetics Clinic can help patients and their families understand the genetic contributions to cancer and develop personalized plans to manage their risk.
“As genetic counselors, we translate the information we find to help families make educated choices,” said Kerry Kingham, MS, CGC, a genetic counselor who explained the process at a presentation sponsored by the Stanford Hospital Health Library. “We provide short-term counseling, offering empathy as we help them to understand the impact of getting tested and their test results. And because we work closely with oncologists, we are able to explain various screening and prevention options.”
Most inherited genetic mutations that cause cancer are autosomal dominant, passed along in the dominant gene. “This means that the person has a 50 percent chance of having the mutated gene passed along—not that 50 percent of these people will get cancer,” said Kingham.
The most common inherited cancers include breast, ovarian, and certain kinds of colorectal cancer. Of the 12 percent of the population who develop breast cancer, the majority (70-80 percent) have sporadic cancer—the kind that develops from environmental factors or other causes. Only about 10 percent have the inherited form of breast cancer. In the 2 percent of the population who develop ovarian cancer, the ratio remains about the same, with about 10-15 percent carrying a genetic mutation.
Women with a BRCA1 gene mutation have a 65 percent chance of developing breast cancer, tend to have early-onset cancer, have a higher risk of developing a second primary breast cancer later on, and are at higher risk for ovarian cancer. The mutation affects about one person in 400 in the general population and about one in 40 in Ashkenazi Jews. A BRCA2 mutation is linked to a higher risk of developing breast cancer and ovarian cancer, and a higher risk for male breast cancer.
Though the BRCA test itself is expensive, Kingham said that insurance usually covers the costs if certain criteria are met. Tests are less expensive for people from the Ashkenazi Jewish population and even less for that group if previous tests have shown that the mutation is already in the family.
Tests are available for two types of inherited colon cancer: hereditary nonpolyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP). People with HNPCC must undergo early and regular screening since they have a much higher risk of developing the polyps that can lead to colon cancer. People with FAP develop thousands of polyps at a very young age and often need to have their colon removed.
Before being tested, counselors go over an extensive list of criteria, check medical records of relatives, and talk to families as a group to clarify details. They look for certain trends and characteristics, such as the first-degree relatives affected, early-age onset, bilateral tumors, or multiple primary cancers. If a woman tests positive for a mutation, counselors will recommend early screening and discuss options like a prophylactic mastectomy or removing the ovaries.
“We’re in the cancer prevention business,” said Kingham, who interviews several generations of a family whenever possible. “We try to provide a balance between prevention and screening, and we work together to get as accurate information as possible. Our goal is to provide clear options for medical or surgical interventions, and to make sure the patient understands the risk before making a medical decision.”
About the Cancer Genetics Clinic
The Stanford Cancer Genetics Clinic offers testing and counseling for people who are concerned about the risk of inherited cancer. The clinic’s specialists help patients and their families understand the genetic contributions to cancer and develop personalized plans to manage their risk. Services include individualized cancer risk assessments based on medical and family history, detailed discussions of options for genetic testing, and recommendations for preventive screening and treatments.
The clinic provides counseling for several types of inherited cancer, including colon, breast, and ovarian.
For More Information:
Cancer Genetics Clinic
Stanford Cancer Center
Cancer Genetics (National Cancer Institute)
Genetic Testing for Breast and Ovarian Cancer Risk (National Cancer Institute)