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Breast Cancer Genetic Testing: What to do With Test Results

After the Shock,Becoming Proactive

By Betsy Lee-Frye

Updated June 11, 2008

(LifeWire) - The decision to undergo genetic testing for breast cancer can be wrenching for everyone involved. But the results of such a test, no matter what they are, can be an empowering call to action.

Genetic testing, which involves taking a blood sample, generally shows whether an individual has one of two gene mutations, BRCA1 and BRCA2, which are linked to an increased risk of developing breast or ovarian cancer. In some cases, a physician may recommend testing for other gene mutations, especially if there is a family history of other cancers. The blood test for BRCA1 and BRCA2 mutations can come back as negative, positive or ambiguous, but interpreting these results is complicated, and experts recommend talking to a doctor or genetic counselor to determine what they mean.

Genetic testing for cancer is most revealing when approached as a family affair. Experts suggest that a relative who has already been diagnosed with cancer (or the disease in question) be tested first for the presence of one of the genetic mutations. If that individual tests positive for a mutation, other male and female members of the immediate family should pursue testing. Men can also carry and pass on BRCA1 and BRCA2 gene mutations.

Negative Results

Interpreting a negative result depends greatly on how many other family members have been tested for the gene mutation. But remember: A negative result does not mean that the individual will never develop breast or ovarian cancer. This test simply indicates whether an individual has an increased risk of developing these cancers as a consequence of harboring a specific mutation.

For an individual with other family members who have tested positive for the gene, a negative test result is called a "true negative." According to the National Cancer Institute, a "true negative" means it is doubtful that the individual inherited the gene mutation. This individual then has the same breast cancer risk ask as any other American, which is about 12%.

However, for those who have a family history of breast or ovarian cancer, but do not have any family members who tested positive for a mutation, a negative result is not as informative. This result could mean one of three things: it could be a "true negative;" the family could have a BRCA gene mutation that is not identified by the test; or the family may have an entirely different gene mutation that is responsible for the hereditary cancer.

A negative result for BRCA1 and BRCA2 gene should not be a license to throw caution to the wind. The existence of other genetic mutations for cancer is possible. Women with a family history of cancer, despite a negative genetic test result, should continue to avoid breast cancer risks, such as alcohol and smoking. Other preventative measures include regular exercise, following standard surveillance recommendations and breast feeding. According to one study, published in The Lancet, for each year a woman spends breastfeeding, her risk of developing breast cancer decreases by 4.3%.

Women without an increased risk of breast cancer should have a mammogram every one to two years, beginning at age 40. For women over 50, an annual mammogram is recommended.

And although there is no clinical evidence supporting the benefits of self or clinical breast exams, the National Guidelines Clearinghouse still recommends these measures of surveillance. Self-breast exams can be performed monthly, and clinical breast exams will usually be conducted during annual checkups or gynecological exams.

Ambiguous Results

Though it is easy to assume that results will either be positive or negative, according to The National Cancer Institute, as many as 10% of women will receive ambiguous results. This result typically means that a gene mutation was uncovered, but it is a variation that has not been scientifically associated with breast or ovarian cancer.

Individuals with an ambiguous result should talk to their doctor or a genetic counselor about their risk factors. These women should also continue with regular mammograms as recommended.

Positive Results

A positive test result can leave a woman and her family reeling. But these results can also be a call to action. Remember, positive test results do not mean a cancer diagnosis.

For women with a positive test result, the increased risk depends on a variety of factors, including age and family history. But for those with a known BRCA1 or BRCA2 mutation, between 35% to 84% will be diagnosed with breast cancer by age 70. The risk of developing ovarian cancer is between 10% to 50%.

With the help of a physician, families who have BRCA1 or BRCA2 mutation can adopt one or more of the following plans:

  • Increased surveillance: According to the Memorial Sloan-Kettering Cancer Center, women with an above-average risk of breast cancer should have clinical breast exams every three to six months and begin annual mammography at least 10 years prior to the earliest age of diagnosis in the family. Some physicians also recommend an annual MRI.
  • Chemoprevention: This term refers to a class of medications designed to prevent cancer in women with an increased risk. Tamoxifen and Raloxifene, commonly prescribed chemoprevention drugs, work by blocking estrogen receptors on pre-cancerous cells that require estrogen to grow. Tamoxifen decreased invasive breast cancer risk by almost 50%, according to a study funded by the National Cancer Institute. This medication was also shown to reduce the risk of noninvasive breast cancer by 30%. Because tamoxifen can affect fertility, the drug is not FDA-approved for women younger than 35. Similarly, Raloxifene is only approved for postmenopausal women.
Physicians suggest that the use of these medications be limited to five years. Chemoprevention drugs can cause many side effects. Women taking Tamoxifen or Raloxifene report hot flashes, changes in the menstrual cycle, nausea, and changes in the amount of vaginal secretions. In addition, Tamoxifen is associated with an increased risk of blood clots, and a slightly increased risk of endometrial cancer. Talk to a physician about weighing the benefits and risks before beginning chemoprevention therapy.
  • Surgical Prevention: Surgical removal of the breasts and ovaries is the surest way to prevent a cancer diagnosis. Experts say the chance of breast cancer is reduced by almost 90% when women choose a prophylactic mastectomy. According to one study of 88 women with a BRCA mutation, nearly 70% opted for surgery. However, many of these women waited several years between genetic testing and surgery; some opting to wait until after childbearing age. In a 2007 study of 106 women who underwent prophylactic surgery, 84% reported satisfaction with their decision. Risks of surgery include swelling or infection, and loss of muscle tone and strength in the shoulder, chest and arm.


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LifeWire, a part of The New York Times Company, provides original and syndicated online lifestyle content. Betsy Lee-Frye is an independent journalist living in Kansas City, Mo. She is a fellow with the Association of Health Care Journalists. Her work has appeared in The Dallas Morning News, Better Homes and Gardens Special Interest Publications and the St. Joseph News-Press.

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