1. What causes cancer?
2. Aren't most cancers due to strong hereditary factors?
3. What's the difference between the terms "genetic" and "hereditary"?
4. If the breast or ovarian cancer on my father's side of the family is due to strong hereditary factors, can I inherit them?
5. If my close relatives had breast cancer after age 50 or postmenopausally, does this mean that the cancers in my family are not due to strong hereditary factors?
6. If both my mother and father were diagnosed with cancer, is my cancer risk very high?
7. Who should have genetic testing to see if they are at increased risk of cancer due to hereditary factors?
8. Are women who have a mother or sister diagnosed with breast cancer at increased risk of breast cancer if they take replacement hormones at menopause?
9. If I have the average woman's risk of 1 in 9, does this mean that of the 9 women at a meeting, one of us is likely to have breast cancer?
10. How important is the size of a breast cancer when it is found?

  Cancers are due to changes in a person's genetic material, the genes. Genes are present in almost every cell of the body, and are responsible for producing the chemicals that make the body grow and develop. The genes are composed of DNA and are located on the chromosomes, with each gene having its own place on its own chromosome.
  Almost all cells contain all the DNA needed to make a complete person. Suppressor genes are one way a skin cell, for example, ensures that only the genes needed to make skin cell products are active. It is as if there is a piano in each cell, with only certain keys allowed to play in different cell types. If several suppressor genes are lost or damaged, the cell may begin unregulated cell growth. It is this unregulated growth that we call cancer.
  The genetic changes responsible for producing a colon cancer of the non-hereditary type are known and shown below (see "Development of Colon Cancer"). These changes occur in a single cell after conception, and need not occur in the order shown.

2) Aren't most cancers due to strong hereditary factors?

  Actually, only 5 to 10% of cancers of the breast, ovary, and prostate are thought to be due to strong hereditary factors. Mutations in the BRCA1 and BRCA2 genes are examples of strong hereditary factors. Another ten per cent of these cancers may be due to moderately strong hereditary factors - mutations in genes with less influence than BRCA1 or BRCA2, or to mutations in several genes (see "Heterogeneity of Breast Cancer" below). As many as 10 to 15% of colon cancers may be hereditary.

3) What's the difference between the terms "genetic" and "hereditary"?

  Genes are present in most cells of the body (called somatic cells), not just the egg and sperm cells. All cancers are due to changes in the genes. Cancers that are not due to hereditary factors are brought about by changes in somatic cell genes that occur after conception. Cancers due to strong hereditary factors result from a change in at least one gene in an egg or sperm cell that occurs before conception, and at least one change in the genes of a somatic cell that occurs after conception. Only a genetic change that occurs in an egg or a sperm cell can be passed from one generation to another.

  An increased hereditary susceptibility to breast and ovarian cancer can be passed through the father's as well as the mother's side of the family. For this reason, both sides of an individual's family must be analyzed.

  Breast cancer diagnosed after age 50 or postmenopausally is found in families with strong hereditary factors. In one study of women with a BRCA1 mutation, for example, about one-third of the breast cancer risk occurred after age 50. Generally speaking, the younger the age at diagnosis, the greater the likelihood that strong hereditary factors are present. However, an older age at diagnosis is no guarantee that strong hereditary factors are not present.

  In assessing risk due to hereditary factors, one does not add relatives from both sides of the family. Instead, the pattern, types of cancers, and ages at diagnosis for each side of the family are taken into account. Since relatively few cancers are due to strong hereditary factors, it is unusual for an individual to have a greatly increased hereditary cancer risk from both sides of the family.

  Individuals who have more than one close relative with cancer, two generations of relatives diagnosed with cancer, relatives with cancers that have occurred in two or more sites, and relatives diagnosed with cancer at young ages may be at increased risk of cancer due to hereditary factors. Before making a decision about whether to be tested, individuals would be wise to have their family history analyzed by a health professional experienced in cancer genetics, and to learn whether testing is available for the cancers of concern to them.
  If testing is available, an individual needs to determine the usefulness of the test in his or her situation. At the present time, even when many individuals in a family have cancer, testing may not provide information about risk, since not all mutations that increase cancer risk are known.

  At least five studies now show that women with close affected relatives who take replacement hormones at menopause are not at increased risk of breast cancer compared to women with similar family histories who do not take hormones.

  Risk information without time is generally uninformative. As the visual below shows (see "Age and Breast Cancer Risk"), the average woman's risk to age 85 is 1 in 9 or 11%. When the average woman reaches age 50 and has not been diagnosed with breast cancer, 2% of her risk is gone and 9% (11 minus 2) remains.

10) How important is the size of a breast cancer when it is found?

  Size is a most important prognostic indicator. In one study, women whose breast cancers measured less than 1 cm (a little less than half an inch, as shown in "Breast Lumps of Different Sizes" below) had a survival of 95% to 12 years. For those whose breast cancers measured up to 1.5 cm, the survival was better than 90% to 12 years. Other studies of small cancers find survivals of better than 90% to twenty years.
  Mammograms can detect about 85% of breast cancers. Therefore, breast self-examination and physician/nurse physical examinations also play an important role in finding a breast cancer at the smallest (and most curable) state.

For more information about hereditary and non-hereditary breast and other cancer risks, genetic testing, and training programs for health professionals in Cancer Risk Assessment, contact: Patricia T. Kelly, Ph.D., Medical Geneticist

Copyright ©1996-2004, Patricia T. Kelly, Ph.D., Cancer Risk Assessment  -  www.ptkelly.com  -  ptkelly@ptkelly.com