Colorectal cancer development and advances in screening

Figures & data

Figure 1 CRC development and screening methods.

Notes: (A) Histological changes of CRC; (B) acquired genetic changes of CRC; (C) effective screening tests for CRC. The temporal development of CRC is indicated from left to right in each panel. Includes methylation of BRAF, KRAS, BMP3, and NDRG4 genes. Data from O’Brien et al.²⁸
Abbreviations: CRC, colorectal cancer; CIMP, CpG island methylator phenotype; CT, computed tomography; FOBT, fecal occult blood test; FIT, fecal immunochemical test; MSI, microsatellite instability; sDNA, stool DNA.

Figure 2 Polyps.

Notes: (A) Flat, serrated polyp. (B) Pedunculated polyp. Photos courtesy of Louis M. Wong Kee Song, MD, Professor of Medicine, Division of Gastroenterology, Mayo Clinic.

Table 1 CRC screening tests

Test	Premise	Sensitivity for CRC	Screening interval	Advantages	Limitations
Colonoscopy	Endoscopic examination of the entire colon	>95%	Every 10 years	High sensitivity, allows visualization of full colon, detection of distal and proximal lesions, can remove lesions at time of detection	Invasive, unpleasant bowel preparation, requires special facilities and sedation, cost, accessibility, need for anesthesia, low patient compliance, risk of bowel perforation or bleeding
Sigmoidoscopy	Endoscopic examination of the distal colon	>95% (distal colon only)	Every 5 years in combination with FOBT	High sensitivity (distal colon only), full sedation not required, can remove lesions at time of detection	Semi-invasive, unpleasant bowel preparation, requires special facilities and sedation, cost, accessibility, only screens distal colon, safety concerns, patient discomfort
CT colonography	Radiologic visualization of the colon, aka virtual colonoscopy	>90%	Every 5 years	High sensitivity, allows visualization of full colon, no sedation needed, detection of distal and proximal lesions	Semi-invasive, unpleasant bowel preparation, requires special facilities, cannot remove lesions at time of detection, radiological safety concerns
FOBT	Enzymatic detection of hemoglobin in the stool	33%–75%	Annually	Accessibility, noninvasive, low cost, detection of distal and proximal CRC	Poor detection of precancerous lesions, cannot remove lesions at time of detection, detects ingested hemoglobin
FIT	Immunochemical detection of hemoglobin in the stool	60%–85%	Annually	Accessibility, noninvasive, low cost, detection of distal and proximal CRC	Poor detection of precancerous lesions, cannot remove lesions at time of detection
mt-sDNA test	Molecular detection of DNA aberrations and hemoglobin	92%	Every 3 years	High sensitivity, accessibility, noninvasive, detection of proximal and distal lesions	Better detection of cancer than precancerous lesions, cannot remove lesions at time of detection

Abbreviations: CRC, colorectal cancer; CT, computed tomography; FOBT, fecal occult blood test; FIT, fecal immunochemical test; mt-sDNA, multitarget stool DNA.

O’BrienMJYangSMackCComparison of microsatellite instability, CpG island methylation phenotype, BRAF and KRAS status in serrated polyps and traditional adenomas indicates separate pathways to distinct colorectal carcinoma end pointsAm J Surg Pathol200630121491150117122504

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