Indications of hereditary risk

How do genes and heredity affect cancer risk for my children?

Genes are made up of DNA, the hereditary blueprint that makes us who we are. We have two copies of each gene. We get our genes from our parents, inheriting one copy of a gene from our mother and another copy from our father. When a parent has a mutation, there is a 50 percent chance of passing on the mutation to each of his or her children, since each child inherits either the normal copy of the gene or the copy with a mutation.

Are all cancers hereditary?

No. In fact, only about 5 to 10 percent of all cancers are inherited. Most cancers are due to an accumulation of damage to the DNA in our cells. This occurs naturally as we age, with most cancers occurring at older ages (50+). The development of cancer is a multistep process. This means that several different changes have to occur in the cell's DNA before cancer develops. An individual who inherits a cancer gene mutation is already one step ahead in this process. Thus, fewer steps have to happen before cancer develops, and cancer may be seen at younger ages than otherwise expected.

What could indicate that I might be at hereditary risk for cancer?

Cancer is a common disease. It is expected that families will have one or more relatives with some form of cancer. Nevertheless, several clues exist to suggest hereditary cancer in a family.

These clues include:

  •     Cancer at an early age
  •     More than one generation with cancers
  •     Same type of cancer in at least two closely related relatives
  •     Multiple primaries (more than one type of cancer in the same person)
  •     Bilateral disease (cancer occurring in both sides of a paired organ, e.g., cancer in both breasts)
  •     Multifocal disease (many primary tumors arising in the same organ)
  •     Rare cancers clustered in the same side of the family
  •     Breast and ovarian cancer in the same side of the family
  •     Breast cancer that occurs in a male
  •     Colon and uterine cancer in the same side of the family
  •     Multiple cologastrointestinal polyps in a young individual (e.g., 10 in a person)

 

The genes involved with cancer can come from either side of the family. Thus, a cancer gene trait may be passed to a daughter through her father who did not have cancer. Accurately interpreting family history information is an essential aspect of genetic counseling.