Is cancer genetic?

Cancer risk is complex. Cancer is so common that we all probably know someone whose life has been affected by one form of cancer or another. A lot of us probably know people who seem to have cancer "running in the family". Cancer can occur in three main ways:

• Sporadic cancers - these are cancers that occur by chance in individuals who have no known genetic risk factors and no significant family history. Approximately 60% of cancers are sporadic.
  
  
• Familial cancers - these are cancers caused by variants in multiple genes and the environment all working together. In this case, each genetic variant causes a slight increase in risk. The overall risk of developing cancer depends on the number of cancer risk genetic variants that a person inherits and what environmental factors interact with those genes. Although these cancers appear to cluster in families, they don’t follow the typical rules of inheritance.
  
  
• Hereditary cancers - these are cancers that are associated with a change in a single cancer susceptibility gene (like BRCA1 or BRCA2). These genes account for a very small percentage of all cancers. In fact, only 5-10% of breast and colon cancer cases are caused by changes in a single gene. Although everyone who carries a change in a cancer susceptibility gene does not get cancer, the risk is increased greatly, usually to 50% or higher. These types of genetic changes are passed on in an autosomal dominant inheritance pattern in families. This means that each child of an individual that carries a gene change in a hereditary cancer susceptibility gene has a 50% chance of inheriting the gene change.

Many people mistakenly think that the risk of cancer is always passed on through families as a single "cancer gene". However, like other complex diseases, changes in many genes that each plays a role in the development of cancer are much more likely to be the cause of familial cancer than a change in a single gene.

The testing that is provided as part of participation in the Coriell Personalized Medicine Collaborative™ study will look at gene changes that contribute to an individual's risk of cancer but WILL NOT look for single genes, such as BRCA1 or BRCA2, known to cause hereditary breast and ovarian cancers or other genes known to cause other hereditary cancer syndromes. If you believe you are at risk of a hereditary cancer syndrome please discuss this with your doctor or a genetic counselor.

nheriting a "cancer gene" does NOT mean you will get cancer

Having a genetic variant associated with cancer does NOT mean that you will definitely get cancer. A genetic variant associated with cancer is simply another risk factor. Just as non-genetic risk factors like smoking or diet impact your overall cancer risk, genetic variants also influence your risk of developing cancer. Knowing that you have a genetic risk and understanding what it means may motivate you to make preventive lifestyle and behavioral changes. It may also encourage you to ask your doctor about other ways to help lower your risk.

Genetic changes can influence cancer treatment

Treatment for cancer is very complex. Two patients with the same type of cancer may respond very differently to the same treatment. While some genes are involved in the risk to develop cancer, other genes are involved in the way our body responds to medicine. Researchers have found gene changes that are associated with a better or worse response to certain cancer-fighting drugs. The CPMC research study hopes to gain a better understanding of the genetic variants that play a role in drug response so that this information can be used to improve the treatment of cancer and other diseases.