Researchers say they have discovered genetic conditions other than Lynch syndrome that may be hereditary causes of colorectal cancer.
When it comes to colorectal cancer, your family’s genetic makeup may play a bigger role than previously thought.
That’s according to a study from The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC – James), which has revealed new data on people under the age of 50 diagnosed with colorectal cancer.
Researchers analyzed data from 450 patients with early onset colorectal cancer, finding that 16 percent of patients — or 1 in 6 — has at least one inherited genetic mutation.
These hereditary mutations increase the risk of cancer.
While the link between colon cancer and Lynch syndrome — a genetic condition that carries a high risk of colon cancer — is well understood, the study shows that Lynch Syndrome is just one risk factor.
The researchers published their findings today in the medical journal JAMA Oncology.
Researchers were somewhat surprised by the numbers, according to Heather Hampel, a professor of clinical, internal medicine at OSUCCC – James, and a principal investigator of the study.
“We knew we’d have a lot of Lynch syndrome as we’ve done a lot of work in that area in the past, and we did confirm that 8.7 percent of cases had Lynch syndrome,” Hampel told Healthline. “So that’s the number one cause of early onset colon cancer. But what was really surprising was that another 8 percent had a different hereditary cancer syndrome.”
Some of these mutations were known colon cancer genes. However, there were others that were less expected, like BRCA1, BRCA2, and PALB2, which are typically associated with breast cancer.
“We feel that at a 16 percent rate of those early onset colon cancer patients having an inherited susceptibility, that it’s time to actually consider recommending genetic counseling and consideration of a multigene cancer panel for all of those patients, which isn’t done currently,” said Hampel. “Right now, doctors typically screen for Lynch Syndrome, and if they don’t see that, or don’t see a lot of polyps, they let it go. But given this data, it appears they all need a broader cancer gene panel, including things like Lynch syndrome.”
Currently, it’s recommended that doctors screen cancerous tumors for Lynch Syndrome at the time of a colon cancer diagnosis.
If the results show a likelihood of Lynch Syndrome, further genetic tests are done to determine if the Lynch syndrome gene is present.
Hampel says this testing should continue, but she also proposes expanded testing.
“In the past, we really kind of neglected the patients whose tumors were less likely to have Lynch Syndrome. They don’t necessarily get any follow-up genetic counseling or genetic testing of their blood to see if they were born with a mutation that gave them an increased risk of cancer,” she said. “This data would suggest that that group needs the counseling and testing just the same as the group whose tumor screening comes back as abnormal, or more likely to have Lynch syndrome.”
Based on their findings, the OSUCCC – James researchers are recommending that genetic testing be expanded for all early onset colon cancer patients.
Hampel points to current National Comprehensive Cancer Network (NCCN) guidelines as a precedent.
“The odds of having a hereditary cancer syndrome if you have ovarian cancer at any age is somewhere between 18 and 24 percent. And we’re getting really close, at 16 percent,” said Hampel. “For those ovarian cancer patients who have an 18 to 24 percent chance of testing positive, the current recommendation is that every single one of them should get genetic counseling and testing. If it’s the current NCCN recommendation for every single ovarian cancer and we’re all striving to achieve that, I think it would be no more difficult to list all of the colon cancer patients diagnosed under age 50.”
While this data could help diagnose a genetic susceptibility to colon cancer early in life, there’s a lack of awareness surrounding this type of cancer.
“We’ve seen what the Angelina Jolie story did for diagnosing hereditary breast and ovarian cancer, and we haven’t had something similar with colon cancer and Lynch Syndrome, so it hasn’t gotten that same level of attention,” said Hampel.
Despite the knowledge gap, genetic testing for colon cancer is widely available, accessible, and inexpensive.
Hampel says most large cities have hospitals where patients can find genetic counselors and geneticists, adding that people in rural areas can access genetic counselling services over the phone.
“There have been dramatic changes in the past three years in testing that’s made it much, much more accessible, and I don’t think people know this,” she said. “As with anything, it takes a little while for people to adjust after the data comes out. I think that there is going to be more data coming out in the next six months as well that’s supportive of this, so I think we’ll get there. It’ll just take a little while.”