Everyone has a risk of developing cancer throughout their life. Cancer is caused by both copies of a gene (or segment of our DNA) in a cell in our body that has mutated and no longer functions correctly. By not functioning correctly, the cell loses control and starts to divide into additional mutated cells. These mutated cells form a tumor, or cancer, which then continues to spread unless removed or treated.
There are a number of ways that two copies of a gene can become mutated to form cancer. Approximately 70% of the time, cancer occurs sporadically. This means that throughout your life, you would have to take two “hits” or gene mutations from living your everyday life. We know that certain environmental factors can cause an increased risk of cancer, such as too much exposure to ultraviolet radiation from the sun, smoking, alcohol, or exposure to certain chemicals. Often in the case of sporadic cancer, people tend to develop cancer later on in life, in their 70’s or 80’s because it takes a lifetime to accidentally acquire those two “hits” to a cell in your body. This is also why everyone has a risk of cancer throughout their life.
In approximately 5-10% of cases, people are born with a hereditary cancer syndrome. This means that a person is born with one “hit” or gene mutation in every cell of their body. All it takes is one additional “hit” from the environment to form cancer in these individuals. Often in families with a hereditary cancer syndrome, individuals are diagnosed with cancer at much younger ages and with specific types of cancer depending on the syndrome. To have a gene mutation that causes a hereditary cancer syndrome in your family means that you have a genetic predisposition to cancer.
For example, there are families who have a hereditary cancer syndrome called Lynch syndrome. Lynch syndrome is caused by a gene mutation in one of five genes: MLH1, MSH2, MSH6, PMS2, or EPCAM. A person with Lynch syndrome is born with a gene mutation in one of these 5 genes in every cell of their body. This means that it only takes one more “hit” from the environment throughout their lifetime to the other copy of the gene to cause cancer. Lynch syndrome causes an increased risk to colorectal, uterine, ovarian, small bowel, and stomach cancers (including a risk of additional cancers). If a person is found to have a gene mutation associated with Lynch syndrome, each family member has a 50% risk to also have the gene mutation. That family would have a genetic predisposition to cancer.
There is one additional category of cancer that also falls into the category of having a genetic predisposition to cancer. Approximately 20% of cancers are familial cancers. This means that we know that a family is at increased risk to develop cancer due to a combination of genetics and environment. However, unlike hereditary cancer syndromes, we don’t have specific genetic components that we can identify. It’s most likely a combination of multiple genetic components. In these circumstances, a person would have a genetic predisposition to cancer and would be medically screened and treated based on their personal and family cancer history.
If you have a strong family history of cancer, have similar cancers running in your family, have members of your family diagnosed with rare cancers, or a personal or family history of cancer at a young age, you may have a genetic predisposition to cancer. It is recommended to meet with a genetic counselor to determine if you need genetic testing. Please contact AT-GC to meet with a genetic counselor.