Genomic Testing May Help Colon Cancer Screening and Treatment Strategies

Thanks to a decade of advances in science and therapy innovations, individuals have more screening and treatment options to fight against colon cancer. One of the more significant advances was the international effort to map the human genome. The Human Genome Project helped unlock the mystery behind the organization of hereditary biological information in human DNA (deoxyribonucleic acid), including both the coding or active and non-coding segments of genetic instruction called genes.

This effort has opened up a whole new field of testing and treatment options for many medical conditions, including preventing or treating colon cancer. Here are some examples:

Stool DNA Testing. Although colonoscopies are still the gold standard, DNA testing of stool (fecal matter from bowels) is an emerging technology in screening for colorectal cancer. Researchers use sensitive laboratory tools to learn the gene sequences of DNA in stool by identifying DNA from cells shed from cancer and precancerous polyps present in the intestinal tract. For example, pre-malignant growths and cancers shed certain DNA genes intact because these segments are not degraded during the digestive process. Clinical studies that use the marker genes have shown a cancer detection sensitivity rate of at least 71% and up to 91%. Although the American Cancer Society endorsed stool DNA testing to detect colorectal cancer, the test is not perfect. Concerns remain about the reliability of stool DNA tests and others of this type relating to the difficulties in detecting the presence of such minute amounts of tumor DNA. Reliability difficulties mean that tests can produce a false positive result if the test indicates cancer is present when it is not or a false negative result if the test indicates cancer is not present when it is. However, for many patients, stool DNA testing can be a helpful resource to a patient that adds to the tests physicians study to fully assess their diagnosis and treatment options.

Gene Expression Testing. Several new tests are being introduced that look at predispositions, or the likelihood for certain biological behaviors to emerge from an individual’s set of unique genetic instructions. Gene expression tests can help doctors predict events like the rate of occurrence of colon cancer or the risk of the spread – or recurrence – of cancer once a malignant tumor is found. For example, one gene-based diagnostic test that has been approved, the Oncotype DX® Colon Cancer Assay, can help patients with stage II colon cancer learn more about how the biological features of their specific tumors might function and how likely it is that a patient’s cancer may recur in the future. The Oncotype DX® Assay analyzes the activity of a specified set of 12 genes within the cells of a patient’s tumor to help predict the likelihood of whether or not that patient’s cancer will recur within three years. Specifically, this test uses RNA (ribonucleic acid) analysis of tumor tissues to measure the presence of genetic products from, or expression of, these 12 genes. This information can help patients and oncologists make more personalized treatment decisions based on the tumor’s specific biological characteristics.

Genetic Counseling. The numbers and availability of genetic counselors has grown in recent years. These trained professionals provide information and support to patients and families who may be at higher risk for certain hereditary forms of colon cancer, such as hereditary nonpolyposis colorectal cancer (HNPCC) or familial adenomatous polyposis (FAP). Simply put, genetic testing can help indicate which family members have an inherited a defective gene — and thus an increased risk of cancer. Genetic results combined with family histories can arm individuals and families with actionable information that can help them become more informed decision-makers.

One thing about the future is certain. The development of gene-based tests and assays will continue to expand. Advancements in the various DNA and RNA expression analysis tests and in correlating these tests with disease states and stages will improve our knowledge about the incidence of colon cancer and other medical conditions. As genomic knowledge grows, communication strategies and touch points between patients, their families, and health care professionals need to grow – to enhance the sharing of information about the dynamic array of screening and treatment options for all cancers, especially colon cancer.