A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is a novel suggestion that no one wants to believe. It is guilty, until found effective. – Edward Teller
The U.S. Department of Health and Human Services recently released its 2020 Healthy People benchmarks aimed at improving the health care of all Americans. These health care objectives are released every decade using evidence-based information with a firm scientific foundation. This year, the 2020 objectives have included new health promotion areas to concentrate on; including Adolescent Health; Blood Disorders and Blood Safety; Dementias, including Alzheimer's Disease; Early and Middle Childhood; Genomics; Global Health; Health care-Associated Infections; Health-Related Quality of Life and Well-Being; Lesbian, Gay, Bisexual, and Transgender Health; Older Adults; Preparedness; Sleep Health; and Social Determinants of Health.1
The sequencing and formation of an initial draft of the human genome was first accomplished in 2001. The explosion of information from the Human Genome Project has increased our understanding of the genetic and molecular basis of a number of human diseases, including a number of common diseases such as heart disease, cancer and diabetes. There are currently more than 1,700 genetic tests available and are growing at a steady rate. The genomic objectives of Healthy People 2020 emphasize the importance of obtaining a family and genetic history as a potential and powerful guide for clinical and public health initiatives. The first genomic recommendation is that women with a family history of breast or ovarian cancer should receive genetic counseling. In 2005, 23.3 percent of women with a family history of breast or ovarian cancer received genetic counseling. Healthy People 2020 would like to increase this to 25.6 percent or a 10 percent improvement.
The second recommendation is to increase the number of patients newly diagnosed with colorectal cancer who obtain genetic testing to rule out Lynch syndrome. Lynch syndrome, also known as hereditary nonpolyposis colorectal carcinoma, was named for Henry T. Lynch, MD, Chair of Preventive Medicine at Creighton University Medical Center.2 This familial syndrome is inherited in an autosomal dominant fashion and predisposes the individual to cancer of the colon, rectum and other organs, including the stomach and small intestine. Women with Lynch syndrome are at higher risk of developing uterine and ovarian cancer.
Lynch syndrome is caused by the inheritance of mutations in genes that assist in the repair of DNA errors that occur during cellular replication. The genes involved include MLH1, MSH2, MSH6 and PMS2 and mutations in any of these genes hamper the cells ability to repair these DNA errors. While mutations in these genes increase the risk, they do not guarantee the development of cancer. It is estimated that 2 to 7 percent of all new cases of colorectal cancer (160,000 per year in the U.S.) are associated with mutations in these genes.
These genomic recommendations are based on the thought that knowing this information will improve the health of involved patients. It is estimated that 85 percent of women with BRCA1 or BRCA2 mutations who undergo prophylactic surgery would reduce their risk of breast and ovarian cancer. Patients with Lynch syndrome who follow screening recommendations for this syndrome could reduce their risk of developing cancer by up to 60 percent. Hence, by increasing one's knowledge through genetic counseling and appropriate testing, the risk of developing cancer in high-risk individuals can be significantly reduced. As more genetic tests become available, their ability to alert us to patients at high risk of developing or having asymptomatic disease will increase for a number of common causes of morbidity and mortality. One difficulty in this process will be the evaluation of these tests and determining their validity and reliability, especially on a population basis. Genetic counseling is extremely valuable in obtaining a detailed family history, ensuring that the appropriate test is ordered and that an appropriate treatment plan is developed in cases with both positive and negative tests. In the setting of a strong family history of cancer but with negative genetic tests, the individual may still be at higher risk of cancer and could benefit from earlier intensive screening. The genomic era of medicine is an exciting time to improve the health of our patients and the people of South Dakota.
REFERENCES
1. Genomics-Healthy People 2020. (2010). Retrieved Dec 7, 2010, from www.healthypeople.gov/2020/default.aspx
2. Douglas JA, Gruber SB, Meister KA, Bonner J, Watson P, Krush AJ, Lynch HT. History and molecular genetics of lynch syndrome in family G: A century later. JAMA 2005;294(17):2195-2202.
©Copyright Keith A. Hansen, M.D.
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