Understanding Cancer Risk
“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 Carbone Cancer Center Genetics 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 genetic changes, or mutations. Thus, 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: 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: Hereditary risks are due to those “cancer genes.” These are high-risk genes that by themselves significantly increase cancer risk. Anyone who tests positive for a mutation in one of these genes, such as BRCA1/2, Lynch Syndrome and many others, has inherited one defective copy of a gene, predisposing them to a much greater risk of eventually having both copies mutated. Testing positive for a hereditary cancer gene does not ensure that the person will develop cancer, but their risk is greatly elevated.
- Familial: 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.
How the Type of Cancer Risk Informs Medical Management
Medical management of cancer risk depends on the type of cancer risk. I’ll use colorectal cancers as an example here. For people with no family history of colon cancer, so those with sporadic/average risk, current screening guidelines recommend a colonoscopy every ten years beginning at age 50. 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.
Family members who test negative are not at high risk despite their family history, so 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 a Cancer Patient or Their Family Members Should See a Genetic Counselor
A healthcare provider needs to send a referral for a patient to be seen by a genetic counselor in the Oncology Genetics Clinic at the UW Carbone Cancer Center. Patients are welcome to initiate that discussion with their physician! The physician can practice in primary care, oncology, surgery, etc. If patients have a family history of cancer, are concerned about their risk or have cancer and are worried about what that means for their relatives, they can contact their physician to see if a referral can be made. Testing is not required to see us; it is only one component of what we do. Much of what we do is to educate patients about inherited risk factors, discuss if genetic testing might be helpful and make cancer screening recommendations.