One of my many curiosities about health and aging well is genetics! We are so fortunate to have genetic testing available to us for many conditions.
Many of us have family members who have died from cancers. Approximately five to ten percent of all colorectal cancers are caused by a heritable mutation. That is a genetic change that can be passed on from parent to child. My father died for colon cancer. While my lifestyle is very different from what I came from, I wanted to know if I could be tested. My insurance will cover the largest portion of the cost.
Other conditions that appear to run in families are not caused by mutations in a single gene. Instead, environmental factors such as dietary habits or a combination of genetic and environmental factors are responsible for various diseases and disorders.
I became aware of testing for colorectal cancer through an article about Lynch Syndrome in a publication that my medical clinic publishes and sends out to their patients. I had no idea that so many cancers can be associated with the development of colorectal cancer. I then made an appointment to speak to a genetic counselor. Which lead to the agreement that I could have the test. That will be done on July 6th. It is a blood test.
The average age for colorectal cancer to be diagnosed in someone with Lynch Syndrome is 45 as compared with the average age of 72 for a new diagnosis of colorectal cancer in the general population. In Lynch Syndrome colorectal cancer is somewhat more likely to develop on the right side of the color. Lynch Syndrome used to be known as “hereditary nonpolyposis colorectal cancer (HNPCC)”.
The two major subtypes of hereditary colon cancer are called familial adenomatous polyposis (HNPCC). In addition, some rare conditions, including attenuated familial adenomatous polyposis (AFAP) and MUTYH-associate polyposis (MAP), have been associated with an inherited risk for colorectal cancer.
Because my sister died from endometrial (uterine) cancer and my father of colon cancer these two cancers are classified as Lynch Syndrome. Lynch Syndrome is an inherited condition that gives a person a higher risk of cancers of the digestive tract, gynecological tract, and other organs. People who have Lynch Syndrome have a significantly increased risk of developing colorectal cancer, endometrial cancer, gastric cancer, ovarian, small bowel cancer, pancreatic cancer, urinary tract cancer (bladder or ureter cancer), kidney cancer, bile duct cancer, certain skin tumors, brain tumors, breast cancer, and prostate cancer (in males).
What causes Lynch Syndrome? While research is still evolving it is known that several genes have been identified that link through several different genes that have the mutations. They are MLH1, MSH2, PMS2 and EPCAM. Most mutations are found in MLH1 and MSH2. Yet not all families that appear to have Lynch Syndrome. Some people will develop changes in these genes that are not inherited, but are related to the aging process and other causes that are not well understood. If a tumor is found to have alterations in these genes, the person’s blood will also be tested for that abnormal gene. If the blood and tumor both have the changed gene, the condition is inherited rather than acquired, meaning other family members could be affected.
Normally, every cell has two copies of each gene; one inherited from the mother and one inherited from the father. Lynch Syndrome follows an what is known as a dominant inheritance pattern, in which a mutation needs to happen in only one copy and one copy of the gene for the person to have an increased risk of acquiring the disease. This means that a parent with a gene mutation may pass along a copy of their normal gene or a copy of the gene with the mutation. Therefore, a child who has a parent with a mutation has a 50% chance of inheriting that mutation. A brother, sister, or parent of a person who has a mutation also has a 50% chance of having the same mutation.
Options exist for couples interested in having a child when they know that one of them carries a gene mutation that increases the risk for this hereditary cancer syndrome. Preimplantation genetic diagnosis (PGD) is a medical procedure done in conjunction with in-vitro fertilization (IVF). It allows people who carry a specific genetic mutation to have children who do not carry the mutation. A woman’s eggs are removed and fertilized in a laboratory. When the embryos reach a certain size, one cell is removed and is tested for the hereditary condition in question. The parents can then choose to transfer embryos that do not have the mutation, PGD has been in use for over a decade, and more recently has been used for several hereditary cancer predisposition syndromes. However this is a complex procedure with financial, physical, and emotional factors for couples to consider before starting. For more information talk with an assisted reproduction specialist at a fertility clinic.
Most colorectal cancer is sporadic, meaning it occurs by chance with no known cause. Approximately 3% to 5% of all cases of colorectal cancer are thought to be due to Lynch Syndrome.
Should my testing come back indicating that I have the genetic factor, I get to have colonoscopies more frequently. I currently go every five years. Colorectal cancer is preventable and treatable. The cure rate is high. With early diagnosis, colorectal cancer can be successfully treated more than 90% of the time. I’m all about prevention.
