Genetic screening determines your risk of developing certain cancers based on inherited genes that, when altered, are associated with cancer. The actual test is just a simple blood test. However, making the decision to be tested, and what to do with the results, is not simple at all.
Genes are pieces of DNA-bits of instructions that tell your body how to function. You're probably most familiar with genes in terms of inherited traits, such as hair and eye color or height. Genes are located on 23 pairs of chromosomes. We inherit each set of 23 from our mother and father.
Researchers have identified two genes directly implicated in an increased risk for cancer: BRAC 1 and BRAC 2 (Breast Cancer Gene 1 and Breast Cancer Gene 2). BRAC 1 is associated with higher risk of breast (for men and women) and ovarian cancer. This gene also slightly increases the chance of developing colon and prostate cancer. BRAC 2 increases your risk for lymphoma, melanoma, and pancreas, gallbladder, bile duct and stomach cancers.
Genetic screening tests your DNA to see if there is a mutation, or alteration. Screening only tells you if you are at higher risk for cancer. It identifies gene mutations, not the actual disease. Having an increased risk of cancer does not necessarily mean you will develop cancer.
All cancers develop from genes that run amuck and replicate without restraint. However, inherited genes only cause five to 10 percent of cancers. If you test positive for the altered BRAC 1 gene, for example, it means that you are three to seven percent more likely to get breast cancer. Physicians order genetic screening most often for women who are at higher risk of breast and ovarian cancer.
If you test positive for BRAC 1or BRAC 2, you may choose to take precautionary steps such as closely watching for cancer symptoms and reducing lifestyle risk factors, such as smoking, alcohol consumption or excessive weight gain. Some women opt for preventative chemotherapy or surgery to remove the breasts or ovaries, which lowers their risks. These steps do not eliminate all risk of developing cancer, however. For some women, simply knowing whether they are at higher risk provides relief and reduces anxiety.
The downsides to genetic testing are primarily associated with emotions and family relationships. You must consider what you will do with the results. Your relatives may not want to know if they are higher risks. You may feel guilty to learn you have passed along an altered gene, or if you don't have the genetic mutation and a family member has cancer. Despite negative screening results, some people still feel uncertain about their risks.
Sources:
http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_Can_ovarian_cancer_be_prevented_33.asp
http://www.cancer.gov/cancertopics/factsheet/Risk/BRCA
http://www.cancer.gov/cancertopics/Genetic-Testing-for-Breast-and-Ovarian-Cancer-Risk
http://www.genetichealth.com/CRC_Genetic_Testing_Colon_Cancer.shtml
http://patient.cancerconsultants.com/Testing.aspx?TierId=1085&LinkId=54237&DocumentId=736
