Handbook of Genetic Counseling/Cancer

Cancer

Cancer Epidemiology Data

Cancer is the uncontrolled growth of cells. All cancers are genetic, but not all are inherited. It is a multifactorial disorder, caused by both genetic and non-genetic factors.
Cancer is a very common disease. 1 in 2 men and 1 in 3 women will develop some form of cancer in their lifetimes. The most common cancer sites are lung, breast, prostate, and colon.
In the U.S., approximately 175,000 new cases of breast cancer are diagnosed each year (50,000 of these are in women under 40).
In the U.S., 1 in 8 women will develop breast cancer over their lifetimes. Average age of developing cancer is 62. 2/3 of the women will be over 55 years old.
Genes are on chromosomes and they come in pairs (1 mom, 1 dad). Autosomal dominant, so 50/50 chance of inheriting the gene. Explain tumor suppressor genes, oncogenes, mutations.
About 5-10% of all breast cancer is hereditary. About 20% of it is familial (combination of different genes and environment). Most cancer is sporadic.
Familial clustering is more common than hereditary breast cancer. A combination of genes from both sides of the family plus environmental factors.
Our job is to figure out where your cancer lies. Of the hereditary type, 2/3 is caused by BRCA1 (45%) and BRCA2 (35%) mutations (increases the risk up to 85%).
Management: mammograms at age 40, physician exam twice a year, self-exams monthly.

A pedigree is our "physical exam". Gives us clues as to whether the cancer is hereditary. It's important to know who has AND who doesn't have cancer.
"Tell me about your experience" or "Tell me what happened"
Very specific questions about the cancer in different family members
Age at diagnosis
Current age & screening practices
Age at death & specific cause of death
Primary site of cancer (type, location, stage, laterality)
Metastasis or any new primary cancers
Methods of treatment/surgery
Any types of precancerous lesions
Ethnic background
Environmental exposures
Lifestyle issues (diet, exercise, stress)
Screening habits of "unaffected" relatives
Any other medical conditions that may be associated with cancer
any family hx of early heart attacks, blindness, deafness, birth defects, or multiple miscarriages
Things that make us suspicious. . .cancer across one or more generations, multiple people affected in the same generation, early age of onset (before 50)
Need a medical release for pathology reports, clinic notes, autopsy reports, death certificates, etc. for verification.

The information in this outline was last updated in 2002.