Most colorectal cancers arise from adenomatous polyps, and a large proportion of patients with adenomas will develop recurrent adenomas. There is considerable controversy regarding the appropriate surveillance interval following initial colonoscopy. Studies assessing predictors for recurrent adenomas will provide valuable information for designing individualized surveillance strategies, particularly for patients with either multiple adenomas or pathologically advanced adenoma. We propose in this application to recruit and follow 2000 patients diagnosed in 1996 to 2001 with incident multiple or advanced adenomas to evaluate the utility of a panel of promising tumor markers in predicting the risk of adenoma recurrence. The tumor markers proposed for this study reflect major events that occur during the formation and progression of adenomas. Specifically, we will evaluate the following four groups of tumor markers in relation to the risk of adenoma recurrence: 1) proliferation and apoptosis, including the apoptosis index (TUNEL assay) and the expression of Ki-67 (Mibl), epidermal growth factor receptor (EGFR), and transforming growth factor B receptor type II (TGF-J3 RI]); 2) genomic instability - loss of heterozygosity (LOH) events on chromosomes 5q, l7p, 15q, ip, and 18q; 3) Wingless/Writ signaling pathway - expression of the CTTNB1 (Beta-catenin gene), Cyclin D1 CMYC, and COX2 gene products; and 4) DNA methylation - methylation status of the promoters of the MLH1, MGMT, CDKN2A/P16, and APC. Study patients will be followed through a combination of telephone interviews and medical chart reviews. Paraffin-embedded blocks of initial adenomas will be retrieved for bioassays of tumor markers. The diagnosis of initial and recurrent adenomas will be reviewed and confirmed by study pathologists. This study is likely to provide valuable information for identifying high-risk adenoma patients for close surveillance and chemoprevention.
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