NEW YORK (Reuters Health) - Blood-based colorectal cancer (CRC) markers might be less sensitive in a real-world screening program than what's been reported in the literature, say the authors of a new systematic review.
The reason, they say, is that reported sensitivity estimates come from clinical studies with a high proportion of advanced cases.
Dr. Hermann Brenner and colleagues at the German Cancer Research Center, Heidelberg, note in their report, published online October 19 in the American Journal of Gastroenterology, that screening populations typically contain more individuals with early stage CRC compared to the clinical trial cohorts, so estimates from the trials must be adjusted.
Their new study tries to accomplish that. Working with data from 73 articles (including 134 evaluations of 55 protein, cytological, mRNA, or DNA markers), the researchers combined stage-specific estimates of sensitivity with the expected stage distribution of CRC in screening settings.
Nearly all the reports were hospital-based. "There was a strong increase in sensitivity by stage in most studies," the authors said. Using the German screening colonoscopy program as a referent, they found a greater proportion of higher stage disease in the study groups.
Adjusting for this difference, the markers' estimated sensitivities for screening were lower than the reported sensitivities in 120 evaluations (90%). "The median absolute reduction in sensitivity after stage adjustment was 9.0% units, and the median relative reduction was 19.5%," the research team reports.
In fact, in most cases, sensitivities dropped below 50%.
"Ideally, the validity of screening tests should be evaluated in the screening setting," Dr. Brenner and colleagues point out. "Where this approach cannot be realized, adjustment of sensitivity to the stage distribution expected in the screening setting should be considered to obtain realistic and comparable estimates of sensitivity."
Source: http://link.reuters.com/xuv32q
Am J Gastroenterol 2010.
Last Updated: 2010-10-27 10:25:22 -0400 (Reuters Health)
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