Screening for Colorectal Cancer

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Abstract
We have three questions about the important fecal occult-blood screening study by Mandel et al. (May 13 issue)1. First, although mortality from colorectal cancer was significantly reduced in the annually screened group, it is not clear whether this gain can be attributed to the selective detection of cancer by screening or to an artifact of the very high rate of false positive results (occurring in 10 percent of those screened each year) and consequent numerous colonoscopies. According to the authors' data, about 10,000 colonoscopies or colorectal examinations were performed in this group of about 15,000 to evaluate positive fecal occult-blood tests. Perhaps the random performance of 10,000 colonoscopies in this group, irrespective of the test results, would have yielded a similar outcome.