Study confirms low rate of incidental findings on CTC

2017 11 15 21 16 4926 Colon Intestine 400

CT colonography (CTC) had a lower rate of incidental findings that required workup than previously suspected, according to research published in the July issue of the American Journal of Roentgenology. These results may help revive the call for Medicare reimbursement of CTC colorectal cancer screening.

Unlike colonoscopy -- the longstanding primary screening option for colorectal cancer -- CTC offers additional imaging of the abdomen, pelvis, and lower thorax and, thus, the potential benefit of extracolonic evaluation, lead author Dr. Perry Pickhardt told But this added advantage has also been perceived as a drawback because it could lead to supplementary workup for incidental findings that may ultimately prove inconsequential.

Experts and policymakers for colorectal cancer screening have raised concerns that a high rate of postscreening workups could unnecessarily raise costs, which would support the decision by the U.S. Centers for Medicare and Medicaid Services (CMS) not to consider reimbursement for CTC screening.

To address these concerns, Pickhardt and colleagues from the University of Wisconsin analyzed data from 44 studies, including nearly 50,000 patients, that reported extracolonic findings on CTC between 1994 and 2017 (Am J Roentgenol, July 2018, Vol. 211:1, pp. 25-39).

The researchers discovered that the average rate of important extracolonic findings reported was relatively low overall. In addition, the rate dropped a statistically significant amount in the studies in which clinicians used the CT Colonography Reporting and Data System (C-RADS) instead of a nonstandardized reporting method (p = 0.009). Using C-RADS also more than halved the rate of follow-up diagnostic testing compared with the nonstandardized method.

Reporting methods for extracolonic findings on CTC
  Nonstandardized reporting method C-RADS classification
Significant extracolonic findings 8.2% 3.6%
Additional diagnostic workup 6.4% 2.5%

"Although there is the potential for unnecessary additional workup related to incidental findings, the reality is that these can be turned into a net benefit," Pickhardt said. "If we can harness the information provided by this 'incidental' data, we can add substantial value, which doesn't exist for colonoscopy and stool-based screening tests."

The meta-analysis additionally revealed that for every year since 2006, the odds of a significant extracolonic finding appearing on a CTC exam decreased by 9%. Furthermore, the extracolonic findings were considerably more common for patients with certain risk factors; the rate of these findings was 2.8% in patients without cancer symptoms, 5.2% in patients with symptoms, 5.7% in seniors (≥ 65 years), and only 2.3% in those younger than 65 years.

"This suggests that CTC is maturing as a colorectal cancer screening test and that use of C-RADS should be encouraged to achieve more uniform and comparable results," they wrote. "The actual rates [of extracolonic findings] for senior screening cohorts appear to be acceptably low, which should be reassuring to the Centers for Medicare and Medicaid Services and other payors."

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