Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: Several investigators have reported an association between low serum cholesterol levels and an increased frequency of colorectal cancer. Because low cholesterol levels may be a result of an established cancer, we have investigated the relation between serum cholesterol levels and the frequency of colorectal adenomas, which are thought to be precursors of colon cancer. We prospectively studied 1083 consecutive patients who underwent colonoscopy (241 of whom were excluded because of malignant disease, chronic inflammatory bowel disease, familial polyposis, or partial colectomy). In the remaining 842 patients, analysis of covariance was performed to evaluate the contribution of serum cholesterol to the risk of colorectal adenoma. Serum cholesterol levels were significantly and positively associated with the frequency of colorectal adenoma in subjects of both sexes. After adjustment for age and body-mass index, this positive association remained significant between the top quintile and the lowest quintile for serum cholesterol, with regard to the total study group (odds ratio, 2.0; 95 percent confidence limits, 1.1 and 3.6) and men only (odds ratio, 2.2; 95 percent confidence limits, 1.0 and 4.8). We conclude that there is not an inverse correlation between serum cholesterol levels and the risk of colorectal adenomas; on the contrary, there appears to be a small positive association.
Adenoma