WASHINGTON — As more clinicians practice computed tomographic colonography, they will learn the language in which to report their findings, Dr. Michael Zalis said at a meeting on CT colonography sponsored by the AGA (American Gastoenterological Association) Institute.
“We need to organize our reporting in response to the growth of CTC,” said Dr. Zalis, a radiologist specializing in abdominal imaging and intervention at Massachusetts General Hospital, Boston.
The American Cancer Society and a task force representing several other medical societies have endorsed CTC as a co-lorectal screening method, which means that Medicare coverage of CTC will likely increase, he added.
There are many benefits to using a standard set of terms to report CTC findings, Dr. Zalis said. Standard language can make patient management easier. For example, as CTC becomes more common, a patient may have an exam performed by one practitioner in one location and a follow-up visit with someone else in another location—even another state.
Common terms not only facilitate comparisons across sites, they also facilitate large-scale analysis of CTC by the government and by insurance carriers, Dr. Zalis noted. But standard CTC reporting terms also help physicians track their personal quality metrics on items such as false-positive rates and call back rates, he said.
The CT Colonography Reporting and Data System (C-RADS) project was a collaborative effort that developed terms and guidelines for CTC with categories for describing colonic and extracolonic findings.
Whether CTC will be regulated in the same way as mammography remains to be seen, but the establishment of C-RADS may prepare clinicians to handle similar regulation if it develops.
“For CT colonography, the target of detection is a precursor to colon cancer, the advanced adenoma, usually defined as a lesion greater than 1 cm in size,” Dr. Zalis said.
“The vast majority of even the intermediate-size lesions that we observe are not the advanced adenomas,” he said. And only about 5% of polyps between 0.6 cm and 1 cm are advanced adenomas, according to findings from large surgical series, he said.
The C-RADS characterization of polyps uses a scale from 0 (inadequate prep) to 4 (colonic mass, likely malignant). For example, a C1 means no visible abnormalities of the colon and no polyps of 6 mm or larger. (See box.)
The C-RADS criteria recommend not reporting diminutive lesions that are less than 6 mm in size.
“Hyperplastic polyps per se are not the target for screening in colorectal carcinoma,” Dr. Zalis said. “We are not being cavalier, but we are going to recognize that the clinical significance of these lesions is very small.”
When a clinician finds intermediate polyps (6–9 mm), the C-RADS criteria recommend reporting the polyps and opting for short-interval surveillance if there are one to two; the criteria recommend considering optical colonoscopy for patients with three or more midsized polyps.
“Polyps grow slowly, and any intermediate polyps tend to be stable and may even regress over time,” Dr. Zalis explained.
Patients with polyps that are 10 mm or larger should be referred for a follow-up colonoscopy, as should patients with three or more polyps in the 6- to 9- mm category, he said.
And a patient with a potentially malignant colonic mass should be sent for a surgical consultation.
The screening interval for optical colonoscopy is 10 years. CTC might approach that at some point, but for now the recommended interval is 5 years, Dr. Zalis said.
“We are early in our experience with CTC and the data aren't there yet to support a longer interval,” but that interval may increase with more data,” he noted.
Extracolonic findings must be documented and classified in the interest of good patient care, although fewer than 10% of patients will have clinically significant extracolonic findings, Dr. Zalis said. “But the findings will be there, so they have to be handled in an appropriate way.
“We have to carefully balance the mandate to identify clinically significant findings with the costs of each false positive,” he said. “We don't want to be causing unnecessary work-ups for obviously benign lesions.”
Although CTC has limitations, an attentive clinician can do a reasonable characterization of extracolonic findings and can reduce the likelihood of extracolonic work-ups and the resulting costs.
The C-RADS classification of extracolonic findings ranges from 0 (technical failure) to 4 (a potentially significant finding, such as a renal mass or liposarcoma. (See box.)
Details of clinically significant findings classified as E4 should be communicated to referring physicians according to accepted practice guidelines, Dr. Zalis said.