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Scope or sample? With colon screening, doctors differ

A new survey has learned that while nearly all gastroenterologists recommend colonoscopy for colon cancer screening, one out of four primary care doctors recommend noninvasive methods.

Gonda Building, Mayo Clinic
The Gonda Building, Mayo Clinic
Rochester Post-Bulletin
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ROCHESTER — Colon cancer is third leading cause of cancer death in the United States, but it is highly treatable when caught early. That is why the U.S. Preventive Services Task Force has given a Grade A recommendation for colon cancer screening among all adults between ages 50 and 75.

This year, the national screening authority lowered that recommendation to 45, thereby broadening the pool of those eligible. But it gave the new cutoff a reduced rating, and critics have argued that expanding the pool may lead to unexpected outcomes.

One of those concerns: diverting resources from the large numbers of Americans over 50 who have yet to be screened.

Incomplete messaging may be to blame. While colonoscopy is often considered the default method of early detection, endoscopy is a tough sell for many. Noninvasive screening methods exist for detecting colon cancer, however, and individual doctor-patient consultations known as shared decision-making have been shown to increase screening rates.

Nonetheless, doctor preferences often direct the course of colon cancer screening.


GI specialists and family practice physicians may have different preferred screening methods — particularly concerning the at-home methods that might appeal to patients reticent to be scoped.

A new Mayo Clinic survey of nearly 1,000 primary care providers shows that while majorities of both specialists and generalists prefer colonoscopy for average risk patients needing screening, general practitioners more frequently recommended at-home tests than did specialists, citing the concerns of patients.

The study, published on Tuesday, Dec. 14, in the journal Mayo Clinic Proceedings, found that while lower GI tract specialists preferred endoscopy 96.9% of the time, among primary care clinicians, that support dropped to 75.6%. One-quarter of primary care physicians recommended noninvasive stool-sample collection methods first.

"T hese findings suggest that primary care clinicians recognize the need to tailor their colorectal cancer screening recommendations to the preferences of their patients, especially with the emergence of new, less invasive options, " says Paul Limburg, a gastroenterologist at Mayo Clinic and the study’s senior author.

Colon screening 101

Invasive screening methods such as sigmoidoscopy and colonoscopy require anesthesia, can cost thousands of dollars and entail a small risk of complications, but are good for five and 10 years, respectively.

Noninvasive colon screening methods include blood and stool sample tests, and an on-site noninvasive test known as CT scanning, or "virtual colonoscopy."

All are required to be covered by medical insurance under the Affordable Care Act, and all have their pros and cons.

The Epi ProColon genetic colon cancer blood test was approved by the FDA in 2016. Drawing blood to screen for colon cancer was greeted in the hope of expanding the pool of those seeking screening, but efficacy concerns include the possibility of false positives, that it will be used for those too old to be screened, and that it may detect cancers that do not reduce mortality.


CT scanning for colon cancer is noninvasive and is good for five years, but requires a colon prep the night before, similar to that for an endoscopy, as well as a visit to a medical center.

Other noninvasive methods include three at-home stool testing kits: FOBT, FIT, and sDNA. The first two are relatively cheap and date back decades, while the latter goes by Cologuard, costs $500, was developed with patented Mayo Clinic research and is manufactured by Exact Sciences.

All require at-home sample collection and must be repeated annually, except for Cologuard, which can be given once every three years. Upon positive diagnosis, at-home collection methods trigger follow-up endoscopy screening.

Just a quarter of the family practice doctors surveyed preferred a noninvasive method, but of those that did, Cologuard was ranked first 12.2% of the time, FIT ranked first 7.3% of the time and FOBT ranked first 4.8% of the time.

Only FOBT — fecal occult blood test — and flexible sigmoidoscopy have highest-level so-called randomized controlled trial (RCT) evidence for reducing death from colon cancer.

"With the availability of multiple screening options with distinct benefits and drawbacks related to effectiveness, access, cost, risk and patient acceptability, it is critical to encourage informed choice and shared decision-making between patients and their health care providers," lead author Dr. Lila Rutten said in a statement.

The survey was funded in part by Exact Sciences through an agreement stipulating editorial independence, along with the Kern Center for Science of Health Care Delivery at Mayo Clinic.

Of its nine authors, a competing interests disclaimer stated, one receives royalties along with Mayo Clinic from Exact Sciences, two were current or former employees of Exact Sciences, and three perform contract work within Mayo Clinic for Exact Sciences.


Additionally, the paper acknowledged the "medical writing and editorial support" of two Exact Sciences employees not named as authors.

Neither Mayo Clinic nor its doctors receive royalties for Cologuard tests ordered for patients.

Paul John Scott is the health correspondent for NewsMD and the Forum News Service. He is a novelist and was an award winning magazine journalist for 15 years prior to joining the FNS in 2019.
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