Radiologists, gastroenterologists disagree about need to remove small colon polyps

December 11, 2008

Recommendations from an Oregon Health and Science Center study have clashed with the findings from a University of Wisconsin trial on the value of polypectomy for small polyps identified during CT colonography. The Oregon study calls for immediate resection while the Wisconsin trial concludes that removal would be costly, risky, and, by definition, unnecessary.

Recommendations from an Oregon Health and Science Center study have clashed with the findings from a University of Wisconsin trial on the value of polypectomy for small polyps identified during CT colonography. The Oregon study calls for immediate resection while the Wisconsin trial concludes that removal would be costly, risky, and, by definition, unnecessary.

The clinical literature shows the detection and treatment of colorectal cancer has become a significant economic burden. Though accurate for colorectal cancer screening, gold standard colonoscopy has drawn low compliance rates, mostly due to its invasiveness. CTC has emerged as a highly sensitive exam for detection of suspicious lesions and has been included by the American Cancer Society as an alternative, noninvasive screening test. Studies have already shown that polypectomy of lesions 5 mm and smaller detected at CTC is not cost-effective. The clinical management of small polyps 6 to 9 mm in diameter, on the other hand, remains controversial.

In the study by Dr. David Lieberman and colleagues at the Oregon Health & Science University's gastroenterology and hepatoloy divisions, researchers enrolled nearly 14,000 patients who underwent colorectal cancer screening at 17 practice sites during 2005. Forty-five percent of patients in this cohort (6360) had polyps, and 94% of them had polypectomies. They found that about one in 15 patients with polyps 6 to 9 mm had advanced adenomas and thus most would need to undergo colonoscopy and three-year surveillance. They published their findings in the Oct. issue of Gastroenterology.

These study findings closely reflect results from other modern screening cohorts and provide convincing support for less aggressive management of small polyps detected at CTC. In spite of this evidence, the study's authors appear to have drawn the exact opposite conclusion, according to Dr. Perry J. Pickhardt, an associate professor of radiology at the University of Wisconsin Medical School in Madison and lead author of the other study.

"After a careful consideration of the risk-benefit ratio for patients with small CTC-detected polyps, we have concluded that the risks and costs of immediate colonoscopy referral outweigh the inherent neoplastic risk of such a small polyp," Pickhardt said.

Pickhardt and colleagues used a decision-analysis model validated in previous studies that helped estimate the clinical and economic implications of performing three-year colorectal cancer surveillance, immediate colonoscopy with polypectomy, or neither. The analysis model on a hypothetical population of 100,000 60-year-old adults with CTC-detected polyps 6 to 9 mm showed that, by excluding large polyps and masses, CTC screening already identifies patients at low risk for colorectal cancer, making colonoscopy for small polyps unnecessary. They published their findings in the November issue of the American Journal of Roentgenology (2008;191[5]:1509-1516).

About 10,000 colonoscopy referrals would be needed for each theoretical cancer death prevented at a cost of nearly $400,000 per life-year gained. Physicians could also expect an additional 10 perforations and probably one death related to these extra colonoscopies. There may be no net gain in terms of lives, just extra costs, Pickhardt said.

"Patients should be allowed to have the choice between immediate colonoscopy and imaging surveillance for one or two isolated small polyps detected at colorectal cancer screening," he said.

For more information from the Diagnostic Imaging archives:

McFarland plots course toward acceptance of CT colonographyCT colonography diagnoses both cancers and osteoporosisCT colonography offers number one choice after failed colonoscopyCT colongraphy's proven clinical worth now invites reimbursement