Colorectal cancer screening is essential
Sunday, August 24, 2014 3:05 PM
This week I want to talk about screening for colorectal cancer (CRC). Fortunately, screening for this type of cancer has become more common due to increased public awareness aided by campaigns such as CDC's Screen for Life www.cdc.gov/cancer/colorectal/sfl/.
It is estimated that there will be 136,830 new CRC cases and 50,310 deaths from CRC this year, making it the third deadliest cancer in men and women over 50 years of age. If caught when the disease is localized to the colon, 90 percent of patients live at least five years after they are diagnosed. However, only 39 percent of people are diagnosed at an early stage.
The good news is that the number of new cases and deaths has continued to drop over the last decade or so. The decreases are likely due to more people undergoing recommended screening, but may also be due to other factors as well.
Warning signs that may indicate CRC include blood in the stool, persistent abdominal pain, change in bowel movements (especially smaller diameter stools), unexplained weight loss and iron-deficiency anemia.
An advertisement that ran in the New York Times a few years ago listed three frightening early warning signs of colon cancer: You feel great; You have a healthy appetite; You're only 50. This ad was designed to let people know they can have CRC without any warning signs.
The risk of developing CRC increases with age (93 percent of cancers occur after age 50). A family history of a sibling or parent with CRC or colon polyps also increases one's risk for CRC, though 75 percent of CRC occurs in patients with no family history.
Inflammatory bowel disease (Crohn's disease & ulcerative colitis) also increases the risk of CRC. Not exercising regularly, eating a diet high in fat and low in fruits, vegetables and fiber, cigarette smoking being obese, or drinking too much alcohol are also risk factors for developing CRC.
Colorectal cancer usually begins as a small nest of abnormal mucus-secreting gland cells in the wall of the colon (large intestine). The cells eventually grow into finger-like projections inside the colon called polyps. These polyps are not cancerous, but they have the potential to transform into cancer. There are two types of polyps - adenomatous and hyperplastic. Adenomatous polyps have the potential to become cancerous, while hyperplastic ones do not.
The goal of any cancer screening program is to either find abnormal appearing cells before they have turned into cancer or when the cancer is very small. There are a number of different ways to screen for CRC and different professional groups have produced various screening recommendations. Descriptions of the various screening methods can be found in the reference link at the end of this article.
CRC screening tests can be divided into those that detect adenomatous polyps and cancer and those that detect only cancer. The former group includes flexible sigmoidoscopy (a scope that visualizes the lower part of the colon), colonoscopy (a scope that looks at the entire colon), double-contrast barium enema (an X-ray procedure where dye and air are inserted in the colon), and "virtual colonoscopy" (an X-ray study using a CT scan to construct a three dimensional image of the colon). Flexible sigmoidoscopy and colonoscopy offer the added benefit of allowing the physician to biopsy and remove polyps or suspicious lesions at the time of screening.
Colonoscopy is certainly the gold standard for detection of CRC, but many patients are sometimes squeamish about having one. There are other less invasive tests that can be done, though they are not as sensitive at detecting polyps and cancer.
Less invasive tests that may detect cancer include high-sensitivity fecal occult blood testing (FOBT) and fecal immunochemical testing (FIT). FOBT is falling out of favor for it involves following a specific diet and submitting multiple stool samples to a doctor or lab where they are tested for microscopic blood.
The FIT test is supplanting the FOBT in most doctors' offices. It has the advantage of not requiring dietary restrictions prior to doing the test and can be performed on a single stool specimen. It is also specific for human blood proteins whereas the FOBT may detect animal blood protein that a patient consumed and give a false positive test. If any of these tests are positive, it is usually recommended that patients have a colonoscopy to locate the source of the blood.
The newest test to gain FDA approval is Cologuard®, a stool test to detect DNA specific to colon cancer cells. This test has some potential problems including a high false positive rate of 13 percent (the test is positive, but the patient does not have cancer). The FIT test has about a five percent false positive rate.
If you are over 50 or have other risk factors, you should speak to your doctor about what test or combination of tests may be right for you. The US Preventative Services Task Force gives its highest "Grade A" recommendation for screening patients ages 50 to 75, whereas it does not recommend screening for those over 75 unless a physician feels there are other circumstances to warrant screening.
With the advent of the Affordable Care Act, all insurance companies are required to pay for recommended screening for CRC with no patient cost sharing such as co-pays or deductibles. However, if a patient has a colonoscopy or sigmoidoscopy and a polyp is found, the patient will likely incur the cost of the biopsy procedure and pathology charges to examine the tissue.
For more detailed information, you can visit bit.ly/1znlju6 for the latest Colorectal Cancer Facts & Figures.
Dr. John Roberts is a Crawfordsville physician and one of the owners of Sagamore News Media which publishes The Paper of Montgomery County. His Daily Health Tip can be found on page A1 of The Paper each day.