Posted 5/6/2009
Making sense of conflicting colorectal cancer screening guidelines
By Robert L. Pompa, MD, assistant professor of Internal Medicine James Cancer Hospital and Solove Research Institute
Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer death in both men and women in the United States. Although most cases of CRC occur in individuals at average risk, there are factors that increase one’s risk for the disease. They include increasing age, African-American race and male gender, as well as personal history and first-degree relatives with CRC.
The issue of CRC screening goes beyond whether a patient should have a colonoscopy. Screening intervals can range from three months to 10 years depending on patient characteristics and risk factors. The variety of screening modalities include CT colography (“virtual colonoscopy”), fecal occult blood testing (FOBT), FOBT plus flexible sigmoidoscopy, barium enema and fecal immunochemical DNA testing.
All things considered, who, at what age and how frequently should individuals undergo CRC screening? This can be a complicated and confusing question for many physicians.
A number of societies offer CRC screening guidelines including the American Society of Gastrointestinal Endoscopy, the American College of Gastroenterology, the American Gastroenterology Association, the U.S. Preventive Services Task Force, the American Cancer Society and the American College of Radiology, but collectively, the guidelines can contain inconsistent opinions about the screening process.
Choosing a Guideline
How does the physician determine which guidelines are best suited for CRC screening of his or her patients?
First, the physician must understand the basis on which particular screening guidelines are based. Important factors to consider for any screening test include ease and availability of the test, false positive and false negative rates, the balance between sensitivity and specificity, and cost. Whenever possible, screening recommendations should be based on evidence from multiple randomized controlled trials demonstrating sensitivity, specificity, ease, cost effectiveness and any reduction of morbidity and mortality. For example, despite advances in endoscopic technology, the only CRC screening program that has been shown to decrease mortality is FOBT, followed by endoscopic evaluation of positive FOBT results.
It is also important to consider the source of the guidelines, as each professional society may interpret screening data differently relative to their particular specialty. Variations in data interpretation may significantly influence screening frequency, cost and modality, and add to the complexity of following CRC screening guidelines. These variations can exist even though the randomized controlled trials cited are the same or similar.
For example, published guidelines from cancer-related organizations may tend to favor a more frequent screening interval, regardless of the screening mechanism because the goal of these organizations is cancer detection. Similarly, gastroenterology societies may advocate more frequent or a more endoscopic-based screening recommendation. Similarly, guidelines published by radiology-based organizations may recommend a more prominent role for radiographic screening modalities.
Screening Methods
The complexities of choosing a CRC screening method can be illustrated by CT colography, which can be a very useful tool in colon cancer screening. Patients and physicians are often drawn to CT colography because it implies a less invasive means of CRC screening. Although this procedure does eliminate the risks of endoscopy initially, it nonetheless requires a complete bowel preparation. When suspected polyps are found, colonoscopy is needed to further evaluate the findings, and if the colonoscopy is not available on the same day, then a second bowel preparation on a different day is needed to complete the evaluation. This may be contrary to the patient’s expectations for screening and may affect the patient’s participation in the screening process and drive up cost.
CT colography may also find extracolonic abnormalities that require further study, which leads to additional, and sometimes unnecessary, follow-up investigations. Other considerations such as sensitivity, specificity, false positive rate, polyp miss rate, cost, interval of screening, radiation exposure, availability and local expertise must also be taken into account.
In summary, following CRC screening guidelines can be challenging. It is important to review the published guidelines and choose those that are best suited for the demographics of your patient population, and the technologic resources and specialty expertise available in your area. This reduces confusion and makes it easier to follow the complex recommendations set forth in these guidelines.
Having good communication and collaboration with a board-certified gastroenterologist is paramount for consulting on special or more complex patients, and it is essential for achieving the highest rate of screening possible for your patient population.
“The complexities of choosing a colon cancer screening method can be illustrated by CT colography … Patients and physicians are often drawn to CT colography because it implies a less invasive means of CRC screening … CT colography may find extracolonic abnormalities that require further study, which leads to additional, and sometimes unnecessary, follow-up investigations.”
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