Are many colorectal cancers due to missed adenomas?

An unknown number of colorectal cancers could be due to missed adenomas during previous endoscopy. Data in the literature are sparse. A large cross-sectional study was done in a prospective database of all patients diagnosed with colorectal cancer.

All consecutive endoscopies over a period of 15 years, in which colorectal cancer was diagnosed were included. All patients who underwent more than one endoscopy and in whom ultimately cancer was diagnosed were studied separately.

Colorectal cancer was diagnosed in 835 patients. Twenty-five patients underwent a previous endoscopy without a cancer diagnosis. These 25 patients were divided into three groups according to the time between the endoscopy in which the cancer was detected and the previous endoscopy. Five out of these 25 patients underwent regular surveillance. Only 11 patients had no argument for regular follow-up. Assuming that these cancers developed from an adenoma than only 11 out of 835 (1.3%) cancers were missed in the adenoma phase. There was no difference in the size of the tumour between the three groups of patients.

In normal daily practice, only a small number of clinically important adenomas are missed. The problem of missed adenomas probably is being exaggerated.