Those with a family history of colorectal cancer should incorporate a genetics evaluation into their prevention plan to determine the potential need for a more proactive screening approach, said an expert from Baylor College of Medicine.
“Approximately 5 to 10 percent of colorectal cancers are attributed to a familial cancer syndrome that significantly increases a person’s lifetime risk of developing colorectal cancer and other cancers,” said Tanya Eble, an assistant professor of molecular and human genetics and a certified genetic counselor in the Adult Cancer Genetics Clinic at Baylor. “When we can identify a syndrome in individuals, they can take more proactive steps such as a prophylactic surgery when needed or more frequent cancer surveillance to reduce their risk.”
Current screening guidelines
Current general population guidelines for colorectal cancer screening recommend a screening colonoscopy every 10 years beginning at age 50.
A colonoscopy is a test that evaluates the inner lining of the large intestines (rectum and colon) for ulcers, colon polyps, tumors and areas of inflammation or bleeding that may be precancerous or cancerous and should be removed.
Early detection is key to improving outcomes, Eble said.
“The good news is that over the last 25 years, colorectal cancer deaths have declined by almost 35 percent due to earlier diagnosis through screening and better treatment,” said Eble.
But there is even more that can be done now thanks to advances in cancer genomics, she said.
“We have been able to identify mutations associated with these familial cancer syndromes that can now be included in testing,” said Eble.
Common familial cancer syndromes, increased risk
The common familial cancer syndromes known to be associated with colorectal cancer are Lynch syndrome (hereditary non-polyposis colorectal cancer, or HNPCC), familial adenomatous polyposis (FAP) and MUTYH–associated polyposis (MAP).
“Lynch syndrome is the most common hereditary colon cancer predisposition and accounts for 2 to 4 percent of all colorectal cancers,” said Eble. “We have effective genetic testing methods available to test for a variety of mutations that cause the syndrome.”
Individuals with Lynch syndrome have a lifetime colorectal cancer risk as high as 80 percent, she said. “The syndrome is also associated with an increased risk of endometrium, stomach, ovarian and a number of other cancers.”
Not everyone with a family history has a familial cancer syndrome passed through their family, she said.
“For example, we have a patient whose father had colon cancer. If the father has a known mutation associated with a hereditary cancer syndrome and our patient is not found to have that mutation then our patient is not at increased risk and does not need extra surveillance,” said Eble. “Our patient would just need to follow general population guidelines.”
Importance of genetic counseling
A person with a family history of colorectal cancer – or any cancer – should consult with a genetic counselor to come up with an individualized screening plan, Eble said.
“We take very detailed family histories – children (and grandchildren if applicable), parents, siblings, nieces/nephews, aunts/uncles, cousins and grandparents on each side (maternal and paternal) of the family,” said Eble. “We are interested in current age or the age at time of death, cause of death, any cancer diagnoses (type of cancer, location on the body, and age at diagnosis). When possible it is helpful to get the pathology report.”
Even if a patient knows very limited information about their family history, a counselor can still work with them to come up with the best strategy for their possible testing and management, Eble said.
The Baylor College of Medicine Adult Cancer Genetics Clinic has two board certified genetic counselors and four medical geneticists who work together to help patients determine their risk, whether genetic testing is appropriate for them, or to assist with management decisions. The clinic team works closely with their clinician colleagues in the College’s NCI-designated Dan L Duncan Cancer Center to coordinate appropriate screening or follow up.
To schedule an appointment, call 713-798-7820.
March is National Colorectal Cancer Awareness Month.