Colon cancer screening: Is there an easier, effective way?



By Monique Tello, MD, MPH, Contributor

Why is a colonoscopy worth the hassle?

Cancers of the colon and rectum are common, and lives can be saved with early detection. Colorectal cancer is the fourth most common cancer in the United States and the second leading cause of cancer death. There are well over a million people living with the diagnosis, and 134,000 new cases are expected this year. About 4% of all adults will be diagnosed with colorectal cancer in their lifetime; having a first-degree relative with colorectal cancer or precancerous polyps, a personal history of polyps, advancing age, obesity, alcohol use, smoking, and African-American race all increase the risk substantially.(1, 2, 3)

The five-year survival rate for these cancers is about 90% when the cancer is caught before it spreads at all, but only 68% when it has started to spread, and 10% when it is widely spread (metastatic).(3, 4) For this reason, experts agree that it makes sense to screen people at average risk starting at age 50 and up to age 75, with the decision to continue screening after that on a case-by-case basis.(3, 4)

According to the 2016 guidelines from the U.S. Preventive Services Task Force (USPSTF), there are six acceptable ways to screen for colorectal cancers and precancerous polyps: procedures like sigmoidoscopy and colonoscopy; special imaging techniques (CT colonography); basic stool tests for blood (because bleeding in the intestine can be a sign of cancer); the FIT test, which is a fancier, more sensitive stool test for blood; and the combined stool DNA test that looks for molecules, gene mutations, and blood. Which test to use depends on the patient’s situation and preferences, and the USPSTF has called for more research in order to be able to make more precise recommendations.(5)

Cologuard: The new kid on the colon cancer screening block

Recently my patients have been asking about Exact Sciences’ Cologuard combined stool DNA test, which was approved by the FDA in 2014. You may have seen it advertised on TV, featuring a cute little talking box. Medicare and Medicaid will cover the entire cost of this test (about $500) once every three years for average-risk people who have no gastrointestinal symptoms.

The test is easy-peasy. One of us goes to the website and prints out the order form, the patient fills in the insurance information, and I sign the paper, which gets mailed to the company. They in turn mail the patient a little box with the stool collection kit. The patient goes about their usual routine, without any change to diet or prep whatsoever, poops into the cleverly designed toilet cover/collection jar, and mails it back to the company within two days. The company runs the tests, and the numerical results from each test component are run through a special equation, with a cutoff score for a positive or negative result.(7)They send the results to me, and then I report to the patient. A positive test means that further evaluation is necessary, and that involves a colonoscopy looking for a polyp or cancer.

Just how good is Cologuard?

Based on the one major study cited,(6) it is pretty darned good: Cologuard detected 92% of colorectal cancers and 42% of advanced polyps. As a comparison, the FIT test detected 74% of cancers and 24% of advanced polyps. So it’s better than the only other real non-invasive option, and without the painful prep, potential discomfort, and potentially serious risks of a colonoscopy or CT colonography. (It is important to know that both of these stool tests are more likely to have a false positive result. That means that the stool test can suggest cancer when there isn’t any, and to know for sure, a patient will need a colonoscopy or CT colonography after all.) Right now, the test is covered by insurance every three years, but more research is needed to know if that is an appropriate interval; eventually, the test may be recommended more or less often than that.

Cologuard sounds so wonderful. And it may actually be, but patients should know that the one major study that provided the data upon which most of the recommendations are based was 100% funded by Exact Sciences, the company that makes the test. Even the one other smaller study showing similar, supporting results was authored by co-inventors of the Cologuard technology and scientific advisors to Exact Sciences.(8) It’s really important to know that, and to take this amazing little talking box with a big grain of salt. I can understand why the USPSTF is calling for more research, and why doctors aren’t abandoning the good old, dependable, but pain-in-the-rear-end colonoscopy as a basic screening test. Yet.

Am I recommending the Cologuard for my own patients? You bet. I have many patients whom I’ve been encouraging to have their colonoscopies for years, and for one reason or another, they have delayed. Or, there are some patients with medical issues for whom a colonoscopy may be logistically difficult or too risky. In their cases, the stool tests are very viable options, definitely better than no screening, and maybe better than traditional screening. We just don’t know for sure yet.


  1. NIH National Cancer Institute: Common Types of Cancer.
  2. NIH National Cancer Institute SEER (Surveillance, Epidemiology, and End Results) data.
  3. Harvard/Massachusetts General Hospital Primary Care Office Insight, chapter on Colorectal Cancer Screening, by Blair Fosburgh, MD; Wynne Armand, MD; Primary Care Operations Improvement Specialist Reviewers: Daniel Chung, MD.
  4. Screening for Colorectal Cancer: Strategies for Patients at Average Risk. Up-to-Date (Wolters Kluwer). Chyke Doubeni, MD, FRCS, MPH. Section Editors: J Thomas Lamont, MD; Joann G Elmore, MD, MPH; H Nancy Sokol, MD.
  5. Screening for Colorectal Cancer: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. Lin JS, Piper MA, Perdue LA, Rutter CM, Webber EM, O’Connor E, Smith N, Whitlock EP.
  6. Multitarget stool DNA testing for colorectal-cancer screening. Imperiale TF, Ransohoff DF, Itzkowitz SH, Levin TR, Lavin P, Lidgard GP, Ahlquist DA, Berger BM. New England Journal of Medicine.
  7. Supplement to: Multitarget stool DNA testing for colorectal cancer screening.
  8. Stool DNA testing for screening detection of colorectal neoplasia in Alaska Native people. Redwood DG, Asay ED, Blake ID, et al. Mayo Clinic Proceedings.

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