Genetic testing

Genetic testing is an often overlooked subject for patients with cancer and their families. It is all too easy to get very involved with treatment decisions and not think about genetic testing at all. However genetic testing can significantly influence your own decision, as well as your family decisions, about treatment and surveillance for recurrence.

Genetic testing for hereditary breast and colon cancer can be performed by a medical oncologist or genetic counselor. These tests are run on your blood at any point in your life (test results do not change with treatment). Results are generally available in a few weeks.

Breast cancer genetic testing
Commonly caused by mutations in the BRCA genes. There are other genes that lead to breast cancer, such as the p53 gene, but the BRCA gene is the most common. It has an especially high frequency in the Ashkenazi Jewish population. Having a mutation in this gene leads to an increased risk of ovarian and breast cancer, and less frequently other cancers such as prostate cancer.
For Ashkenazi Jewish women, family history suggesting increased risk includes having 1 first-degree relative or 2 second-degree relatives on the same side of the family with breast or ovarian cancer.
For non–Ashkenazi Jewish women, family history suggesting increased risk includes:
Having two first-degree relatives with breast cancer one of whom received the diagnosis at age 50 years or younger
A combination of at least 3 first- or second-degree relatives with breast cancer regardless of age at diagnosis
A combination of both breast and ovarian cancer in first- and second- degree relatives
A first-degree relative with bilateral breast cancer
aA combination of at least two first- or second-degree relatives with ovarian cancer regardless of age at diagnosis
A first- or second-degree relative with both breast and ovarian cancer at any age
A history of breast cancer in a male relative (yes, men can get breast cancer too!)

What is the point of getting genetic testing for the BRCA mutation? If you tested positive but you have never had either breast or ovarian cancer, what you do next will depend on your risk tolerance. Carriers of a mutation in BRCA1 have a 50 to 85% lifetime risk of breast cancer and a 20 to 40% lifetime risk of ovarian cancer, and an increased incidence of prostate CA. BRCA2 has similar risks of breast cancer, but only a 10% risk of ovarian CA. Both BRCA1/2 increases the risk of male breast cancer (6% lifetime risk for BRCA 2).
So in terms of risk reduction of breast and ovarian cancer, the decision often boils down to screening for these cancers versus prophylactic surgery to lessen the incidence of breast and ovarian cancer.
Screening:
for optimal detection of breast cancer, in addition to mammogram and ultrasound breast, MRI of the breast are now recommended.
For detection of ovarian cancer, although our current testing methodology just is not that accurate for detection of early ovarian cancer, commonly a examination will be supplemented by a transvaginal ultrasound, abdominal ultrasound, and the (somewhat nonspecific) tumor marker CA125.
Prophylactic surgery:
overall, this is a very painful question to address especially in younger woman. A prophylactic bilateral mastectomy (removal of both breasts) will reduce the risk of breast cancer, though not to 0%, since a small residual amount of breast tissue will always be left after the operation. Similarly, a prophylactic bilateral salphingo-oophorectomy (removal of both ovaries and fallopian tubes) will reduce the risk of ovarian cancer to single digit percentages. Do these techniques work to help women live longer? Yes. A study published in 2010 showed that the combination of prophylactic mastectomy and prophylactic oophorectomy at age 40 improved survival more than any single intervention, yielding 24% survival gain for BRCA1 and 11% for BRCA2 mutation carriers.

Colon cancer genetic testing
There are two types of tests available: one for a common syndrome called hereditary non-polyposis colorectal cancer (HNPCC, or Lynch syndrome) and one for a rare syndrome called Familial Adenomatous Polyposis (FAP).
Features of HNPCC
it is caused by genetic mutations in the hMLH1 or MSH2 or MLH6 genes
Consider testing if you or a family member has colon, rectal, or uterine cancer at an age <50. It is a familial syndrome of colon, rectal, and uterine cancer. Several other types of cancers such as ovarian and stomach may be seen. However, note that you may not have any family history of cancer and still have the genes linked to this syndrome. Notably, if you or your relatives have this gene it may not express itself, so even if you have this gene you may not be destined to get cancer. What is the point of testing for this gene in yourself or in family members who do not have cancer? Earlier and more frequent screening with colonoscopies, pelvic ultrasounds would be performed you do have this genetic mutation. While having more frequent colonoscopies and dotting at a younger age certainly is not anyone's idea of fun, please note that many of these cancers are curable if caught early! A few frequent questions on genetic testing: 1) Can the information used from genetic testing be used to deny me insurance? The information cannot be used to deny you health insurance, but unfortunately can raise your life insurance rates. 2) Will testing be covered by my insurance carrier? Generally speaking, the companies that run these tests will first check with your insurance company if these tests are covered prior to running the test. If the test are not covered, the company should inform you about the cost of the test before they actually run it, to see if you wanted.

 






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