“Cancer genes” or “family history of cancer” are terms we often hear associated with cancer or when thinking about one’s cancer risk. But even people with no family history of cancer can develop the disease.
UW Health | Carbone Cancer Center Genetic Counselor Angela Tess, MS, CGC, explains the different genetic risks associated with cancer and how risk assessment helps clinicians inform patients to make treatment decisions.
Assessing cancer risk
Our cells are under tight control, making sure they grow and divide when they are supposed to, or not grow and divide when they are not supposed to. Cancers can arise when that control is lost due to harmful genetic changes, or mutations. Genetics plays an important role in assessing an individual’s cancer risk and informs prevention, screening and treatment decisions.
The three types of cancer risk
Sporadic risk
Sporadic risk is the risk due to “bad luck,” or risk that does not have any family component. Sporadic risk includes the natural ageing process, because our cells are more likely to acquire mutations and not repair them as we get older. These risks may also be due to personal environmental exposures, such as unprotected sun exposure or tobacco use.
Hereditary risk
Hereditary risks are due to those “cancer genes.” These are high-risk cancer genes that by themselves significantly increase cancer risk if they have a mutation. Anyone who tests positive for a mutation in one of these genes, such as BRCA1/BRCA2, the Lynch syndrome genes and many others, has inherited one defective copy of a gene, predisposing them to a much greater risk of eventually having both copies mutated. Cancer begins to develop when both gene copies are mutated. Testing positive for a hereditary cancer gene does not ensure that the person will develop cancer, but their risk is greatly elevated.
Familial risk
Familial cancer risk is due to a mix of shared genes within a family as well as shared environmental or sporadic risk. These shared genes by themselves do not alter risk significantly, but they do work in concert with sporadic risk factors, such as sharing the environment where we grew up or sharing health behaviors.
Medical management
Medical management of cancer risk depends on the type of cancer risk. As an example, for people with no family history of colon cancer (those with sporadic or average risk), current screening guidelines recommend a colonoscopy every ten years beginning at age 45. For people who test positive for Lynch Syndrome, a hereditary disease that increases the risk of developing colon, uterine and ovarian cancers at a younger age, we recommend very different screening guidelines, such as a colonoscopy every year beginning at age 25. We also discuss the possibility of a hysterectomy with women who have Lynch Syndrome. And we would recommend that relatives of someone with Lynch Syndrome be tested for the mutation to know if they should receive early screenings.
When Lynch Syndrome is diagnosed in a family, what about the relatives who test negative? In this situation, family members who test negative for Lynch syndrome are not at high risk for cancer, despite their family history. We would recommend the regular screening schedule for them.
Of course, some families have a history of colon cancer with no clear hereditary component. For those patients, we would go over their family history, decide if genetic testing might be useful and help determine the screening plan that is right for them.
When to see a genetic counselor
A healthcare provider needs to send a referral for a patient to be seen by a genetic counselor at the UW Health | Carbone Cancer Center. Patients are welcome to ask their physician, including their primary care physician or their cancer care team, including their oncologist. If patients have a family history of cancer and are concerned about their risk or have cancer and are worried about what that means for their treatment and/or their relatives, they can contact their physician to see if a referral can be made. Testing is not required. The genetic counseling team educates patients about inherited risk factors, discusses whether genetic testing might be helpful and makes cancer screening recommendations.
