Type 2 diabetes and the risk of colorectal adenomas: Black Women's Health Study

Evidence for the association of type 2 diabetes mellitus (DM) with colorectal neoplasms is contradictory, and African Americans have been underrepresented in the studies published to date. In a nested case-control study (1995-2009), we examined DM and insulin therapy as risk factors for colorectal adenomas in African American women enrolled in the ongoing Black Women's Health Study. From women reporting ever having undergone a gastrointestinal endoscopy, 917 cases of colorectal adenoma were compared with 2,751 controls without a colorectal polyp, matched on age and follow-up time. Cases were verified by medical record review. We used multivariable logistic regression analyses that included DM exposures and selected confounders. There were no overall associations between DM and adenoma risk or between insulin use and adenoma risk. However, DM without insulin use was inversely associated with risk of colon adenomas (odds ratio (OR) = 0.71, 95% confidence interval (CI): 0.52, 0.97) but not rectal adenomas. DM was inversely associated with adenoma risk in women older than 55 years (OR = 0.64, 95% CI: 0.44, 0.91) but not in women 55 years or younger (OR = 1.24, 95% CI: 0.81, 1.89). Future research should attempt to replicate the unexpected inverse association of DM with colon adenoma risk among older African American women.

Ethnic differences in the anatomical location of colorectal adenomatous polyps

The ratio of right- to left-sided colonic cancer is increasing, but data on the distribution of its usual precursor lesion, the colorectal adenoma, are contradictory. Therefore, we investigated the prevalence of right- and left-sided colorectal adenomatous polyps from January 1, 1970, to September 30, 1989, using the study design of "epidemiologic necropsy" and the autopsy files of The Johns Hopkins Hospital. Compared with the decade of the 1970's, the 1980's showed a slight decrease in the overall prevalence of right-sided adenomas (6.4 per 1,000, 95% confidence limits 4.7-8.8 vs. 5.1 per 1,000, 95% CL 3.6-6.5), but a marked decrease occurred in left-sided adenomas (11.8 per 1,000, 95% CL 9.3-14.3 vs. 6.7 per 1,000, 95% CL 4.8-8.6). As a result, the ratio of right-sided to left-sided adenomas increased from 0.55 in the 1970's to 0.77 in the 1980's. This increased ratio occurred in both sexes, although prevalences were lower in females, and in whites. Unexpectedly, blacks had a ratio of right-sided to left-sided adenomas greater than unity in both the 1970's and 1980's (1.19 vs. 1.79) due to a relatively high prevalence of right-sided adenomas (5.8 per 1,000, 95% CL 3.6-8.0 in 1970's; 5.8 per 1,000, 95% CL 3.3-8.3 in 1980's), but low prevalences of left-sided adenomas (4.9 per 1,000, 95% CL 3.0-6.8 in 1970's; 3.2 per 1,000, 95% CL 1.2-5.2 in 1980's). The overall adenoma prevalence in blacks was lower than in whites. We conclude that the right-sided predominance of colorectal adenomas in blacks suggests ethnic differences in the pathogenesis of colorectal adenomas. This observation may have important implications for secondary prevention of colorectal cancer.

Colorectal polyps in the Upper Galilee

This study of colorectal polyps is based on 129 patients in whom 241 colorectal polyps were diagnosed and excised by colonoscopy in the Gastroenterology Unit of a hospital in the Upper Galilee, Israel, between 1 July 1984 and 30 June 1987. The male:female ratio was 2:1. Anemia was demonstrated in 7% and positive Hemoccult II test (Smith Kline, USA) in 64%. The types of polyp were 58% adenomatous, 25% hyperplastic and 15% inflammatory. Adenomatous polyps were larger than the other types (chi 2 = 13.24, P less than 0.01), and were more frequent in the left colon than inflammatory polyps (chi 2 = 4.67, P less than 0.05). The annual incidence of colorectal polyps and the percentage of colonoscopies that revealed polyps were highest for Jews of European/American origin (5.3/10,000, 26%) compared with Jews of Israeli and Asian/African origin and Arabs (2/10,000, 6%; 1.3/10,000, 12%; and 1/10,000, 9%, respectively). These data confirm findings of other investigators showing a higher incidence of colorectal polyps in European/American Jews than in other ethnic Israeli groups.

Site-specific distribution of large-bowel adenomatous polyps. Emphasis on ethnic differences

The anatomic distribution of adenomatous polyps occurring in the large intestine of 98 consecutive patients was studied. Fifty-two of the patients were black and 46 were white. Seventy-nine percent of lesions in whites were found in the distal colon and rectum, whereas in blacks this occurred in only 47 percent. The difference was significant (P less than .01). Black patients also displayed a greater frequency of synchronous polyps and had a higher incidence of previous colorectal polyps. The findings suggest that the total colonic surveillance is essential in black patients to adequately screen for large-bowel neoplasia.

Adenomas, metaplastic polyps and other lesions of the large bowel: an autopsy survey

Out of 1,014 large intestines examined, adenomatous polyps were encountered in 170 (16.8%) and metaplastic polyps in 67 (6.6%). Both types of polyps were more prevalent among the Chinese than the Malays and Indians. The prevalence rates corresponded to the relative risks for large bowel cancer for the respective ethnic groups. This suggests that causative factors such as dietary influence which are common to adenomatous polyps and cancer of the large bowel are operating at different levels among the different ethnic groups in Singapore. There are however, several factors between adenomatous polyp and colorectal cancer which are not congruent suggesting that the relationship between these two lesions though close is not a simple or direct one. On the other hand, the present study has shown several similarities between the epidemiological characteristics of metaplastic polyps and cancer of the large bowel. It is speculated that the causative factor(s) for metaplastic polyps may occur in association with carcinogen of the large bowel, but has an independent action. Consequently, while the metaplastic polyp may not itself be regarded as a premalignant lesion, the possibility that it may be a marker for increased risk for colon cancer is not excluded. Ulcerative colitis is rare in Singapore, and is not considered an important lesion in the pathogenesis of large bowel cancer in this country.

Adenomatous polyps and atherosclerosis: an autopsy study of Japanese men in Hawaii

It is generally accepted that most colorectal cancers arise from adenomatous polyps and most coronary heart disease is caused by severe atherosclerosis. In order to compare the frequency of these disease precursors in men of Japanese ancestry in Hawaii, the degree of atherosclerosis of the aorta and coronary arteries was estimated by the panel method in 288 male autopsy subjects. The extent of atherosclerosis was then compared in men who did or did not have adenomatous polyps as determined at autopsy. The degree of atherosclerosis of the coronary arteries and aorta was positively and significantly related not only to the presence of adenomatous polyps, but to their size, multiplicity, and degree of atypia as well. This study suggests that shared environmental events could account for the development of severe atherosclerosis and adenomatous polyps. At the same time, it has been observed that hawaii Japanese men experience colon and rectal cancer rates higher than those of US Whites, but their coronary heart disease (CHD) rates are intermediate between the low rates of Japan and the high rates of the US white population. These differences in disease trends and differences in the serum cholesterol and fat intake of Hawaii Japanese men with CHD and colon cancer have suggested that men with these diseases represent different subsets of the westernized Japanese population. If CHD and colon cancer occur in different subsets of this population, they must stem from the accumulation of other risk factors superimposed upon the initiators of their precursor lesions.