Colon cancer screenings save lives

By Davis Sim, M.D., Ph.D.

For The Register-Guard

Cancer prevention, screening and early detection programs have been among the most beneficial health care practices implemented in the United States, saving countless lives every year.

Cancer screenings are tests performed on healthy individuals without any symptoms. The tests either prevent cancer or detect it early, when the chances for successful treatment are highest. With March being Colon Cancer Awareness Month, it is important to highlight the progress, as well as issues, surrounding colon cancer prevention.

Colorectal cancer is the third most common cancer diagnosis in both men and women in the United States. The American Cancer Society estimates that 140,250 new cases of colorectal cancer will arise in 2018. Overall, the lifetime risk of developing colon cancer in both men and women is about 4 percent to 5 percent. Decades ago, these numbers were much higher. Since 2000 we have seen significant declines in the number of colon cancer cases per year. Among people older than 50, this number has decreased by 30 percent to 40 percent. In persons above the age of 65, the decrease has been even greater.

Much of this has been attributed to the advent of colon cancer screening. Of the many methods available for screening, only one is truly preventive — colonoscopy. It is considered the gold standard, because not only can you detect early colon cancer, but also remove pre-cancerous polyps, called adenomas, and thereby prevent colon cancer from occurring.

However, there are other options for screening, such as stool-based tests that detect blood (the fecal immunochemical test, or FIT) or the recently approved blood-DNA marker test, Cologuard. Both stool-based tests do a good job of detecting early colon cancer, with the latter being superior to the former. Cologuard not only detects blood but also nine DNA biomarkers that have been associated with colon cancer. The FIT test needs to be done on a yearly basis to be effective; Cologuard needs to be done every three years.

The stool-based tests have two disadvantages. First, if the tests are positive, a colonoscopy will be required. And second, they are much less effective at detecting pre-cancerous polyps.

Though I am a staunch advocate for colonoscopies as a screening tool, it is important to understand that there can be drawbacks, as with everything else we do in medicine. Across all health care fields, we have been trying to make improvements to ensure that consistent, high-­quality care is being delivered to all.

Colonoscopy is no different. One issue being targeted is the variation in performance and outcomes among endoscopists, the specialists trained in the use of imaging equipment used during colonoscopies. This has led to the development of ideals, or “benchmarks,” that every endoscopist should achieve to ensure that high-quality care is always being delivered.

The single most important benchmark is the adenoma detection rate, or ADR. This is the frequency in which adenomas are detected in asymptomatic, average-risk individuals. Higher ADRs have been correlated with decreased risk of colon cancer, regardless of gender. For every 1 percent increase in ADR, there is a 3 percent reduction in colon cancer incidence and a 5 percent reduction in colon cancer death.

Based on multiple studies, the minimum target for overall ADR is 25 percent — 30 percent in men, and 20 percent in women. That is, endoscopists should be finding adenomas in a quarter of the colonoscopies they perform. Studies have shown that patients whose colonoscopies are performed by endoscopists with ADRs of less than 20 percent have a 10 times higher risk for post-colonoscopy cancer than if their endoscopists have ADRs of greater than 20 percent.

It is now the standard of care that every endoscopist should be following his or her ADR, as well as other measures of quality, and ensure that they are above the established benchmarks. Patients should have an expectation that whoever is performing their colonoscopy should be above these benchmarks. Do not hesitate to ask.

Colon cancer doesn’t just occur in March — it occurs year-round, without regard for gender, race or creed. There are still 30 percent to 40 percent of those above the age of 50 who do not get screened. At the end of the day, whatever method is chosen, go get colon cancer screening. It really does save lives.

Davis Sim, M.D., Ph.D., is a physician at Eugene Gastroenterology.




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