Written by SMH Genetic Counselor Nicole Wood
When cancer is caused by abnormal genes passed from parent to child, it is referred to as “hereditary cancer.” About 5% to 10% of breast cancers are inherited, and most of those are linked to mutations in two genes, BRCA1 and BRCA2.
While the BRCA1 and BRCA2 genes have been at the forefront of hereditary cancer research for many years, genetic testing has expanded at a rapid pace in the last decade. It has progressed from “cherry picking” the genes that most likely explain patterns of cancer within a family, to simultaneously testing for a long list of genes known to be associated with increased cancer risk. When a person is tested for many genes, providers use a “panel test.”
What ‘Panel Tests’ Can Tell Us
A standard hereditary cancer panel test evaluates 35 to 84 different genes, each one playing an important role in the body. These tests go far beyond examining BRCA1 and BRCA2 to assess a predisposition to developing cancer — and go beyond looking for indicators of breast cancer; the panel tests also evaluate genetic risks for melanoma and ovarian, colon, uterine, stomach and pancreatic cancers, and more.
For example, a mutation in the STK11 gene may indicate elevated risk for breast, ovarian, colon, uterine, pancreatic and stomach cancer. Likewise, a mutation in the BRCA1 gene may indicate up to an 87% lifetime risk to develop breast cancer, a 63% lifetime risk to develop ovarian cancer, an elevated risk to develop pancreatic cancer, and a 16% risk to develop prostate cancer. These risks are dependent on many factors, such as age, family history and lifestyle habits. In most cases, someone’s true risk is significantly lower than the maximum.
Talking with a genetic counselor offers a more an individualized risk assessment as they are specifically trained to take into account all aspects and risk factors. There are many factors that are evaluated when considering if there may be a hereditary predisposition to cancer in the family, and genetic counselors can ensure that the test ordered is appropriate and covered by insurance.
‘Cancer doesn’t run in my family’
Having a genetic mutation is not a guarantee that you will develop cancer. In fact, many of the risks associated with hereditary cancer syndromes are less than 50%. There is a greater chance of someone never developing any cancer, than someone being diagnosed with one.
In these cases, a genetic susceptibility to cancer can “hide” within a family, being passed from generation to generation, with many people never developing a cancer. This is especially true in small families. When there are fewer people in the family, there may not be an obvious pattern of cancer. If your family has more men than women, there also isn’t likely to be an obvious pattern of breast cancer, even though there may be a predisposition running through the family.
There is also a common pattern of secrecy within families, especially in regards to medical information and cancers. If your family isn’t the type to be open with a cancer diagnosis, there may be cancers in the family that you are unaware of.
Genetic testing allows your physicians to learn about any potential predisposition early, so you don’t have to wait for a cancer to be present to be aware of the risk in your family and you can be proactive about prevention.
‘Cancer Protection’ Genes
Each of the genes tested for on hereditary cancer panels are ‘cancer protection’ genes in one way or another, and each protects several parts of the body. If one of these cancer protection genes has a mutation in it, it may not function correctly, leaving each organ it’s meant to protect vulnerable to cancer.
Having a mutation in one of these genes does not mean someone will definitely get a cancer, as each part of your body has several layers of built-in protection; however, it may increase the likelihood of developing a cancer as you get older.
When a mutation is found in one of these genes, a genetic counselor can analyze the results and estimate the likelihood of developing each of the associated cancers. That type of information makes a big difference in tailoring a screening and prevention plan specifically to an individual and his/her family — especially for those considering risk-reducing strategies such as preventative surgeries.
Many people, including physicians, only consider genetic testing when there is a very obvious family history — and typically when it involves breast cancer. However, half of the genes evaluated in a panel test are unrelated to breast cancer, but they indicate high risks for other cancers such as prostate, colon or uterine.
Approximately 10% of all cancers are hereditary, not just breast cancers. If you are one of those 10%, it has significant implications for you and your family.
Nicole Wood, MS, CGC, is the only licensed and board-certified genetic counselor serving Sarasota County and its surrounding communities. Specialty trained in oncology genetic counseling, Wood works closely with the multidisciplinary Genetic Counseling and Education team at Sarasota Memorial to provide expertise for patients’ clinical care. If you would like to learn more about hereditary cancers, or are concerned about the cancers in your family, call 941-917-2005.