Genetic tumor testing recommended for colorectal cancer patients
Of the 143,000 patients with colorectal cancer diagnoses annually in the United States, up to 25% have a familial risk of colorectal cancer. A new guideline from the US Multi-Society Task Force on Colorectal Cancer recommends genetic testing of tumors for all newly diagnosed cases of colorectal cancer.
Their consensus statement was published in Gastroenterology (2014; doi:10.1053/j.gastro.2014.04.001). They made specific surveillance and management recommendations for those affected by Lynch syndrome, a genetic condition and the most common cause of inherited colorectal cancer, accounting for approximately 3%, or more than 4,000, of the newly diagnosed cases in the United States each year.
They recommend universal genetic testing of the tumors for evidence of mismatch repair (MMR) deficiency in patients with newly diagnosed colorectal cancer for several reasons. First, using clinical criteria and prediction models to identify patients with Lynch syndrome has less than optimal sensitivity and specificity. Second, it has been shown to be cost effective for the diagnosis of Lynch syndrome. Finally, universal genetic testing has greater sensitivity for identification of Lynch syndrome compared with other strategies, including Bethesda guidelines or a selective tumor testing strategy.
Patients whose tumor shows evidence of MMR deficiency, have a known MMR gene mutation in the family, who meet clinical criteria for Lynch syndrome, or who have a 5% or greater personal risk for Lynch syndrome based on prediction models should undergo a genetic evaluation for Lynch syndrome. Germline genetic testing can confirm a diagnosis of Lynch syndrome in the patient, can determine the status of at-risk family members in families in which disease mutation has been found, and can direct the management of affected and unaffected persons.
Patients with Lynch syndrome are at an increased risk of developing colorectal cancer, as well as cancers outside of the colon, including endometrial cancer, ovarian cancer, gastric cancer, and urinary cancer. The US Multi-Society Task Force on Colorectal Cancer recommends that annual history, physical examination, and patient and family education regarding the risk of cancer should start at age 20 to 25 years. In addition, additional screenings that begin at age 20 to 25 years are recommended.
Two treatments are recommended for patients affected with Lynch syndrome. The first is removal of the large intestine, which is the primary treatment for patients affected by Lynch syndrome who have colon cancer or precancerous colon polyps that cannot be removed during colonoscopy. Less extensive surgery can be considered for patients older than 60 to 65 years. The second is aspirin therapy, which growing evidence suggests may be beneficial in preventing cancer in Lynch syndrome patients.
In the United States, colorectal cancer is a major health problem. It is the second leading cause of cancer death, causing nearly 51,000 deaths each year. Environmental causes and inheritance play varying roles in different patients with colorectal cancer. About 20% to 30% of colorectal cancer patients appear to have a familial risk, and a minority has a genetic mutation that contributed to the development of the disease.