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Cancer Genetics

Understanding Genetic Testing for Cancer

10/18/2000

Question:

What is involved with genetic testing for cancer? Is it expensive since it is most often not covered by insurance? Does it detect all kinds of cancers? I`m 57 and constantly worrying about getting/having cancer. I have chronic pain but am afraid to go to the doctor. My mother died of breast cancer when she was 57. I have regular mammograms and pap smears. I worry that those tests are missing something.

Answer:

Genetic testing for cancer is not appropriate for everyone. At this time, genetic testing is offered only to individuals and families with a strong history of cancer. The cancer genetic tests now available are specific for certain types of cancer, such as hereditary breast cancer or colon cancer, and are not tests designed to screen for all types of cancer.

The first step to identify high-risk families, which could benefit from specific cancer genetic testing, is to look for some features in the family history. Such features include:

1) Cancer that occurs at an early age. For example, the average age for diagnosis of breast cancer in the general population is 56 (the age at which you report your mother had breast cancer). In true hereditary cancer families, the age of onset is often younger than age 50, sometimes even in the 20s and 30s.

2) Having multiple family members with cancer in several generations (for example, having a mother as well as other close maternal relatives with breast cancer). 3) A clustering of certain types of cancer in a family (such as breast cancer and ovarian cancer; or colon cancer and uterine cancer).

4) A primary cancer occurring in paired organs (breast cancer occurring in both breasts).

5) Rare cancers (for example, male breast cancer or kidney cancer).

For families that meet even some of these criteria, cancer genetic counseling would be recommended. Genetic counselors provide information about the causes, patterns of inheritance, and implications of genetic testing. They provide a cancer risk assessment by taking a detailed cancer family and medical history (and documenting the cancer diagnoses) to determine the likelihood that a cancer susceptibility gene(s) could be the cause of the cancer in a family. If the level of risk is significant (say 10% chance or more), then specific genetic testing is offered.

The reasons for defining who would benefit from genetic testing, or not, depends on many factors. At this time there are only a handful of genes (less than 20 genes) known to be involved with hereditary cancer, and which are available for testing. The costs of these tests vary greatly, ranging from $300 - $2,800. In each instance the ability of insurance to cover the costs of cancer gene testing differs. Some insurance plans pay for a significant proportion of the cost of testing (say 70-80%); other plans provide minimum coverage. In cases where genetic testing is appropriate for the family, genetic professionals work with the insurance company to determine the level of individual coverage for the specific test.

In all, only around 5-10% of families meets criteria for which cancer genetic testing may be of benefit. As cancer is common, the majority of families (even those with a close relative with cancer but without other significant cancer family history) would most likely not benefit from cancer gene testing. It is possible that in these families with non-hereditary cancer, further research may uncover "weaker" susceptibility cancer genes but at this time these tests are not available.

In lieu of genetic testing, individuals and families such as yours would benefit by practicing good cancer screening. The American Cancer Society (ACS) recommends that at your age you should have a cancer-related checkup every year to include examinations for cancers of the thyroid, mouth, skin and lymph nodes, and an examination of the ovaries. The checkup should also include health counseling (such as tips on quitting smoking). In addition, you should participate in colorectal cancer screening beginning at this time. This should include annual fecal occult blood tests (testing the stool for blood) and either flexible sigmoidoscopy every 5 years or colonoscopy every 10 years. The ACS recommends that women receive breast cancer screening including monthly breast self-examination and annual clinical breast examination performed by a doctor beginning at age 20. Annual mammography should begin at age 40. All women over age 18 or who are sexually active should receive regular gynecologic care including annual pelvic examination and Pap test.

Having available cancer screening on a routine basis is the best method to detect early signs of cancer. It is felt that mammography becomes a better screening tool for detection of breast cancer as a woman gets older, as the breast tissue becomes less dense. Along with clinical examination, and breast self-examination, the chance of early detection and therefore cure of breast cancer increases.

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Response by:

Kevin   Sweet, MS, CGC Kevin Sweet, MS, CGC
Cancer Genetic Counselor
College of Medicine
The Ohio State University

Judith A Westman, MD Judith A Westman, MD
Associate Professor, Clinical Internal Medicine, Pediatrics and Medical Biochemistry
College of Medicine
The Ohio State University