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March is National Colorectal Cancer Awareness Month. According to the Centers for Disease Control and Prevention, colorectal cancer is the second leading cause of cancer deaths in the U.S.
Individuals with an inherited condition called Lynch syndrome have an 80 percent chance of developing colorectal cancer during their lifetime. Shilpa Grover, MD, MPH, of the Division of Gastroenterology, explains the relationship between Lynch syndrome and colorectal cancer.
What is Lynch syndrome?Lynch syndrome is the most common inherited syndrome that can increase a person’s risk for colorectal cancer; it accounts for 2 to 5 percent of all colorectal cancers.
Individuals with Lynch syndrome tend to develop colorectal cancer at an early age. The average age at diagnosis is 45 years, nearly two decades earlier than colorectal cancer in the general population.
Individuals with Lynch syndrome also have a higher risk for developing other cancers, such as cancers of the stomach, pancreas, upper urinary tract, skin and brain, than the general population. Women are at increased risk for cancer of the uterus and ovaries.
What causes Lynch syndrome?It is caused by an inherited defect in the mismatch repair genes that are responsible for fixing errors in DNA. This defect in mismatch repair genes leads to accumulation of genetic damage and eventually cancer.
What have researchers discovered about Lynch syndrome?Genetic testing can confirm the clinical diagnosis of Lynch syndrome. However, genetic test results may be indeterminate. Individuals with indeterminate genetic results remain at increased risk for cancer, and intensive cancer screening is still necessary.
Interestingly, in a study, we found that despite undergoing genetic testing, many patients with indeterminate results were falsely reassured, and therefore greatly underestimated their cancer risk.
As commercial genetic testing becomes widely available, interpreting test results is likely to become more complex. This is why it is important for patients to undergo comprehensive genetic counseling with a qualified individual to discuss results and treatment recommendations.
What advice would you like to share?It is important for people to discuss their family cancer history with their primary care physician. This includes the type of cancer, age that cancer occurred and family history of colorectal polyps.
Adults with Lynch syndrome should undergo colorectal cancer screening yearly beginning at age 20 to 25. Screening allows for removal of polyps and has been shown to decrease colorectal cancer incidence.
Women with Lynch syndrome should have an annual vaginal ultrasound and/or endometrial biopsy starting at age 25 to 35 years. Screening for stomach and upper urinary tract cancers may also be recommended in patients with a family history of these cancers.