Small adenomas detected during fecal occult blood test screening for colorectal cancer. The impact of serendipity
D. F. Ransohoff and C. A. Lang
Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510-8025.
Yearly fecal occult blood testing (FOBT) has been recommended for men and
women over age 50 years as part of a screening regimen intended to reduce
colorectal cancer mortality. The primary targets of screening are early,
surgically curable colon cancers and large adenomatous colon polyps;
however, screening may sometimes reveal only small adenomas (ie, less than
1 cm in diameter). To assess the rates and mechanisms of FOBT detection of
small adenomas, we performed quantitative analyses utilizing estimates of
adenoma bleeding rates and FOBT sensitivity and specificity. The analysis
suggests that the mechanisms of detection of small adenomas is often chance
or serendipity. This occurs when an FOBT result is "falsely" positive
because of diet or non-neoplastic gastrointestinal bleeding and leads to
colonoscopic discovery of a nonbleeding small adenoma. Nevertheless, small
adenomas remain undetected in most persons who have them, even if repeated
yearly FOBT screening is done. The identification of persons with small
adenomas should not be assumed to be an important beneficial outcome of
FOBT screening, because the clinical significance of small adenomas is not
clear, the mechanism of detection is serendipity, and only a minority of
persons with small adenomas are identified. The current recommendations to
perform periodic surveillance colonoscopy following removal of small
adenomas detected during FOBT screening should be reexamined.
