Colorectal cancer is the second most common cancer and cause of cancer-related deaths in the United States, accounting for about 50,000 deaths in 2017. The lifetime risk of its occurrence is estimated to be one in 21 men and one in 23 women. Its incidence has declined 24 percent over the last 30 years and by three percent per year between 2004 and 2013. This decline in incidence is due to improved screening methods. Also, because of better screening, the five-year survival rates for patients with colorectal cancer has increased, from 48.6 percent in 1975 to 66.4 percent in 2009. When detected at a localized stage, the five-year survival rate is over 90 percent. Unfortunately, it is only diagnosed early in 39 percent of patients. It is essential to screen people when they have no symptoms, as symptoms such as gastrointestinal or rectal bleeding, unexplained abdominal pain or weight loss, persistent change in bowel movements, and bowel obstruction typically occur in advanced disease when it is less amenable to cure.
The American Cancer Society recommends beginning screening at age 45. Earlier screening should be done in those with a family history of the disease. For reasons not yet known, the incidence of colorectal cancer is increasing in white males under age 50. Based on current trends, by 2030 the incidence of colorectal cancer is expected to increase by 90 percent in adults ages 20 to 39, and by 28 percent in those 35 to 49. For many years, screening for colorectal cancer relied on the fecal occult blood test, or FOBT. This involves putting a small sample of stool on guaiac paper and adding a drop of “developer” (hydrogen peroxide) on it. The presence of blood in the sample will turn the paper blue. This is done on three consecutive stool samples over three days on an annual basis. This should not be done at the time of a digital rectal examination or if there is rectal, urinary, or vaginal bleeding. Dietary and medication restrictions are critical to this test. Consuming red meat, which contains hemoglobin, and certain vegetables (radishes, turnips, cauliflower, cucumbers) that contain peroxidase will cause a false-positive test. Vitamin C inhibits heme peroxidase activity and will cause a false-negative test.
More recently, fecal immunochemical testing, or FIT, has replaced the FOBT. Media advertising for a FIT called Cologuard is widespread. Most experts recommend FIT every one to two years. It is imperative to follow the directions of the home-based FIT carefully. If the FIT is positive it is important to get a colonoscopy as quickly as possible, as waiting may give a small, localized tumor time to grow. Colonoscopy is not only the gold standard of colorectal cancer screening, it also can biopsy suspicious lesions and remove polyps. It can be done with or without sedation (although I can’t imagine having one without sedation). In the absence of a positive family history of the disease or a history of removal of pre-cancerous polyps, colonoscopy should be done about every ten years. Complications of colonoscopy are rare, but do include bowel perforation (four in 10,000 cases) and significant intestinal bleeding (eight in 10,000).
Colorectal cancer is both detectable and preventable with proper screening. Doctors and patients need to pick a screening method that the patient is comfortable with and will adhere to.
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