Handbook of Genetic Counseling/Cancer
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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.
Cancer Pedigree Questions
- 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.