As DNA testing becomes more affordable and available, many physicians are arguing for its inclusion as part of routine preventive medical care. For the past several years, genetic testing has been utilized to inform treatment strategies in certain cases, particularly for patients with cancer. In addition, the Food and Drug Administration has approved several drugs that target mutations known to cause cancer.
Incorporated into primary care, genetic testing can play a key role in the concept of precision medicine, which aims for early disease detection and treatment, as well as prevention of disease altogether. The Geisinger health system conducted a large-scale MyCode research study, allowing patients to opt into having their genome sequenced.
Through the detection of any disease-related gene mutations, doctors can recommend specific preventive action steps to patients. The health system enrolled more than 230,000 patients in the study, providing sequencing to help detect roughly 59 gene abnormalities that are correlated with 30 diseases, half of them cancers.
Another 33 percent of the gene variants have been associated with cardiovascular disorders such as early heart attacks, strokes, and abnormal heart rhythms. The remaining gene variants are correlated with conditions such as Fabry disease, an enzyme disorder, and cystic fibrosis. When patients learn of a gene variant through routine sequencing, they receive actionable recommendations to mitigate risk. For example, a patient who learns of a mutation in the BRCA2 gene, which has been tied to an increased risk of ovarian, breast, prostate, and pancreatic cancer, can opt for early and more frequent cancer screenings.
Previously, routine genetic testing was cost-prohibitive, as only around 2 percent of healthy people who are screened for actionable mutations end up having them. As the cost of genetic testing continues to fall, however, the clinical usefulness of such tests has become more apparent. Cancer treatment, especially when diagnosed in its later stages, is far more expensive than prevention.
Along with BRCA mutations, genetic testing can detect a number of genetic flaws associated with cancers. Lynch syndrome, for example, is caused by alterations in five genes and has been shown to increase the risk of stomach, bile duct, colorectal, and liver cancers. Likewise, a mutation in the TP53 gene causes Fraumeni syndrome. Individuals who have this mutation have a higher risk for brain cancer, leukemia, and soft-tissue sarcoma.
The early detection of all of these cancers leads to better outcomes. According to the American Cancer Society, colon cancer that is diagnosed before it has spread has a 90 percent survival rate after 5 years. Once the cancer has metastasized, however, the survival rate is just above 70 percent. In a 2014 study, women diagnosed with a BRCA1 or BRCA2 mutation who elected to have their ovaries removed decreased their risk of ovarian, fallopian tube, and peritoneal cancer by 80 percent.
Heart disease, the leading killer of adults in the United States, can also benefit from routine genetic testing. In healthy adults without symptoms, inherited genetic mutations increase the risk of irregular heartbeats that can cause heart attacks. Similarly, individuals with a family history of hypercholesterolemia, a form of high cholesterol caused by a mutated gene that makes "bad" cholesterol, have a 500 percent increased risk of heart disease.
Overall, the inclusion of genetic testing in routine medical care can leverage knowledge to improve diagnoses and outcomes. Particularly for individuals at risk of developing certain types of cancer, DNA testing can provide actionable recommendations for preserving patients’ health.
