Cigarette smoking, alcohol, and the risk of colorectal adenomas

Derivation and validation of a nomogram incorporating modifiable lifestyle factors to predict development of colorectal adenomas after negative index colonoscopy

This retrospective cohort study aimed to identify baseline patient characteristics involving modifiable lifestyle factors that are associated with the development of colorectal adenomas, and establish and validate a nomogram for risk predictions among high-risk populations with negative index colonoscopy. A total of 83,076 participants who underwent an index colonoscopy at the Tianjin Union Medical Center between 2004 and 2019 were collected. According to meticulous inclusion and exclusion criteria, 249 subjects were enrolled and categorized into the primary and validation cohorts. Based on the primary cohort, we utilized the LASSO-Cox regression and the univariate/multivariate Cox proportional hazards (Cox-PH) regression parallelly to select variables, and incorporated selected variables into two nomogram models established using the multivariate Cox-PH regression. Comparison of the Akaike information criterion and the area under the receiver operating characteristic curve of the two models demonstrated that the nomogram model constituted by four covariates retained by the LASSO-Cox regression, including baseline age, body mass index, physical activity and family history of colorectal cancer (CRC) in first-degree relatives, performed better at predicting adenoma-free survival probabilities. Further validation including the concordance index, calibration plots, decision curve analysis and Kaplan-Meier survival curves also revealed good predictive accuracy, discriminating ability, clinical utility and risk stratification capacity of the nomogram model. Our nomogram will assist high-risk individuals with negative index colonoscopy to prevent colorectal adenoma occurrence and CRC morbidity with improved cost-effectiveness.

Wine consumption and colorectal cancer risk: a meta-analysis of observational studies

There were inconsistent results with respect to the correlation between consumption of wine and the development of colorectal cancer (CRC). We carried out a meta-analysis to investigate this issue. We included observational studies on the aforementioned relationship according to a literature search of Embase and Pubmed from inception till 28 February 2017. The summary relative risk (SRR) and 95% confidence intervals (CI) were calculated using a random-effects model. A total of eight case-control and nine cohort studies were identified, involving 12 110 CRC cases. The study showed that wine drinking was not associated with any greater risk for CRC (SRR=0.99, 95% CI: 0.89-1.10; Pheterogeneity<0.001) compared with nondrinkers. The subgroup analyses indicated that null associations were observed in men and women for colon and rectal cancer. Neither light to moderate (<2 drinks/day; SRR=0.93, 95% CI: 0.80-1.08, I= 69.2%) nor heavy (≥2 drinks/day; SRR=1.00, 95% CI: 0.86-1.16, I= 39.9%) consumption of wine was associated statistically with CRC risk. This meta-analysis suggests that any wine consumption was not associated with the risk of CRC. Null associations were shown in men and women for colon and rectal cancer.

A Multicenter Study of Colorectal Adenomas Rationale, Objectives, Methods and Characteristics of the Study Cohort

Background and Aims

The Multicenter Study of Colorectal Adenomas (SMAC) is a retrospective-prospective cohort study involving four Gastrointestinal Endoscopy Units in Italy. The main aim of the study is to evaluate the relationship between clinical and pathologic information at index colonoscopy and subsequent incidence of adenoma and colorectal carcinoma. We report the rationale, objectives and methods of the study, including patient characteristics at initial presentation.

Methods

All patients were consecutively identified from the endoscopy registries of the four Centres from January 1, 1985 to December 31, 1992. Inclusion criteria were: age 18-69 years, endoscopy performed with adequate toilette at least up to the rectosigmoid junction, and removal of all detectable polyps. Exclusion criteria were: familial adenomatous polyposis, inflammatory bowel diseases, adenocarcinoma in adenoma with infiltrated margins, previous invasive cancer at any site, colon resection and geographic inaccessibility.

Results

Out of 20,071 patients who underwent endoscopy at the four Centres, 11,959 fulfilled the eligibility criteria (5,892 males and 6,067 females, mean age = 51.1 ± 11.6 years). The main reasons for exclusion were age (n = 4,020) and previous or present colorectal cancer (n = 2,389). Symptoms were the most common reason for referral (72.3%), while post-polypectomy follow-up and positive fecal occult blood accounted for most of the remaining cases. A pancolonoscopy was performed in 3,088 patients (25.8%), while a left-sided endoscopy was performed in 7,887 (66%). A total number of 4,810 polyps were removed from 2,699 patients (2,994 adenomas, 1,580 hyperplastic polyps and 236 polyps lost after resection). A significant association (p < 0.001) between age and the endoscopic findings was observed. The subjects without polyps (n = 9,198) had the lowest age (mean = 49.9; 95%CL = 49.6 - 50.1) followed by the patients with hyperplastic polyps (n = 661; mean age = 52.3; 95%CL = 51.5-53.1), and the patients with adenomas (n = 1,732; mean age = 56.2; 95%CL = 55.8 - 56.6), and the patients with hyperplastic polyps and adenomas (n = 306; mean age = 57.2; 95%CL = 56.3 - 58.2). Polyps were diagnosed more frequently in males than in females (28.6% versus 17.0%; p < 0.0001).

Conclusion

This study provides some insights in the natural history of colorectal cancer and stresses the need to develop adequate strategies in the follow-up of subjects after either positive or negative colonoscopy.

Melanosis coli in patients with colon cancer

INTRODUCTION

Melanosis coli is a benign lesion affecting the mucosa of the large intestine. There is a relationship between the presence of melanosis and anthraquinone laxative use. Melanosis coli is also observed in patients with colon cancer, but there is doubt whether these two conditions are related.

AIM

To analyze the correlation between melanosis and colon cancer.

MATERIAL AND METHODS

We analyzed retrospectively 436 patients undergoing colon cancer surgery. There were 246 women and 190 men. Patients were divided into three age groups: under 50 years, between 51 and 65 years, and over 66 years. We analyzed sections of the cancer and intestinal mucosa from the tumor's proximal (2-5 cm) and distal (8-10 cm) zone.

RESULTS

Melanosis coli was present in 52 patients, which represents 11.9% of patients with colon cancer. More often it was present in women. The most common location of melanosis and colon cancer was the terminal part of the large intestine. In patients below 50 years of age in both sexes melanosis coli did not occur. In men, melanosis was more common in the age group over 66 years. Intensity of pigmentation was higher in the tumor's distal zone.

CONCLUSIONS

The incidence of melanosis coli increases with age, similar to that of colon cancer. Melanosis was not present inside tumors, in almost half of the cases it was not present in the proximal zone, and the degree of pigmentation increased in distal zone. The cause-effect relationship between melanosis coli and colon cancer remains uncertain.

Development and validation of a clinical score for predicting risk of adenoma at screening colonoscopy

BACKGROUND

Currently, no clinical tools use demographic and risk factor information to predict the risk of finding an adenoma in individuals undergoing colon cancer screening. Such a tool would be valuable for identifying those who would most benefit from screening colonoscopy.

METHODS

We used baseline data from men and women who underwent screening colonoscopy from the randomized, multicenter National Colonoscopy Study (NCS) to develop and validate an adenoma risk model. The study, conducted at three sites in the United States (Minneapolis, MN; Seattle, WA; and Shreveport, LA) asked all participants to complete baseline questionnaires on clinical risk factors and family history. Model parameters estimated from logistic regression yielded an area under the receiver operating characteristic curve (AUROCC) used to assess prediction.

RESULTS

Five hundred forty-one subjects were included in the development model, and 1,334 in the validation of the risk score. Variables in the prediction of adenoma risk for colonoscopy screening were age (likelihood ratio test for overall contribution to model, P < 0.001), male sex (P < 0.001), body mass index (P < 0.001), family history of at least one first-degree relative with colorectal cancer (P = 0.036), and smoking history (P < 0.001). The adjusted AUROCC of 0.67 [95% confidence interval (CI), 0.61-0.74] for the derivation cohort was not statistically significantly different from that in the validation cohort. The adjusted AUROCC for the entire cohort was 0.64 (95% CI, 0.60-0.67).

CONCLUSION

We developed and validated a simple well-calibrated risk score.

IMPACT

This tool may be useful for estimating risk of adenomas in screening eligible men and women.

Alcohol intake, smoking, and colorectal adenoma

Background:

Colorectal cancer is the third most common cancer in Korea. Because colorectal adenoma is a precursor lesion of colorectal cancer, primary prevention of colorectal adenomas may be important for reducing morbidity and mortality from the disease. The aim of this study is to examine the association of alcohol consumption and cigarette smoking in relation with colorectal adenoma in a cross-sectional study of Korean adults.

Methods:

A total of 366 participants who underwent colonoscopy were included (113 cases and 255 controls) in this study. Information on alcohol intake and cigarette smoking was collected from structured questionnaires. The odds ratio (ORs) and 95% confidence intervals (CIs) were calculated using the multivariate logistic regression models.

Results:

Alcohol intake was associated with a higher prevalence of colorectal adenoma in men; compared to non-drinkers, ORs (95% CIs) were 11.49 (2.55–51.89) for 10–20 g/day of alcohol intake and 14.15 (3.31–60.59) for â 20 g/day of alcohol intake (P for trend = 0.003). There was a weaker association of alcohol intake for women than men; however, there was a suggestive increase in the prevalence of colorectal cancer in women. Cigarette smoking was not associated with colorectal adenoma, but we cannot rule out the possibility that this was due to low statistical power.

Conclusion:

Our study provides evidence to suggest that alcohol intake may contribute to colorectal adenoma in the Korean population. Our study results demonstrate that a larger epidemiologic study is needed.

Cigarette smoking and outcomes after allogeneic hematopoietic stem cell transplantation

Abnormal lung function is a known risk factor for poor outcomes in the allogeneic hematopoietic stem cell transplantation (HSCT) population, although the specific causes of these abnormalities have not been well explored. There is limited data on the effect of cigarette smoking on transplantation outcomes. We conducted a retrospective observational cohort study of 845 consecutive patients age ≥ 18 years who underwent allogeneic HSCT at the Seattle Cancer Care Alliance/Fred Hutchinson Cancer Research Center. Smoking exposure was defined by quit time, smoking status (never, former, and current), and log(2)-transformed pack-years. The main outcomes were time to respiratory failure within 100 days of transplantation, relapse, and nonrelapse mortality. In multivariable analyses, a 2-fold increase in pack-years smoked was associated with an increased risk of early respiratory failure (hazard ratio [HR] 1.33, 95% confidence interval [CI] 1.09 to 1.64, P = .006). This association was observed independent of pretransplantation lung function. A 2-fold increase in pack-years smoked was associated with an increased risk of relapse, but this finding was not statistically significant (HR 1.16, 95% CI 0.92-1.46, P = .21). An association was not observed between cigarette smoking and nonrelapse mortality. Cigarette smoking is associated with an increased risk of respiratory failure and relapse within 100 days of allogeneic HSCT. The association with respiratory failure is mediated in part by abnormal lung function before transplantation and likely through other mechanisms as well. Given the adverse effects associated with cigarette smoking before transplantation, future studies should focus on obtaining accurate smoking histories, tracking prospective changes in smoking status, and assessing the benefits of tobacco cessation on outcomes in this population.

Relation between normal rectal methylation, smoking status, and the presence or absence of colorectal adenomas

BACKGROUND

Colorectal cancer (CRC) is 1 of the leading causes of death in the Western world. CRC develops from premalignant lesions, chiefly colorectal adenomas. Currently, the most accurate and recommended screening method for finding colorectal adenomas is colonoscopy performed on all individuals aged>50 years. However, the costs and risks associated with this procedure are relatively high. The objectives of the current study were to correlate epigenetic alterations that occur in normal rectal mucosa, smoking status, and age with the presence or absence of concomitant colorectal adenomas and to assess the potential clinical value of methylation in normal rectal biopsies as a screening assay for the presence of polyps and, hence, the need for a full colonoscopy.

METHODS

One hundred thirteen normal rectal mucosal biopsies from 113 patients were studied. DNA was extracted, modified with sodium bisulfite, and subjected to real-time quantitative, methylation-specific polymerase chain reaction analysis for the following genes: adenomatous polyposis coli (APC); cadherin 1, type 1, E-cadherin (epithelial) (CDH1); estrogen receptor 1 (ESR1); cytokine high in normal 1 (HIN1); hyperplastic polyposis protein 1 (HPP1); O-6 methylguanine-DNA methyltransferase (MGMT); neural epidermal growth factor-like 1 (NELL1); splicing factor 3B, 14-kDa subunit (p14); cyclin-dependent kinase (CDK) inhibitor 2B (inhibits CDK4) (p15); retinoic acid receptor beta (RARβ); somatostatin (SST); tachykinin, precursor 1 (TAC1); and tissue inhibitor of metalloproteinase (TIMP) metallopeptidase inhibitor 3 (TIMP3). Data were then analyzed using several proprietary software programs.

RESULTS

By using several sets of genes, clinical characteristics, and multivariate analyses, the authors developed a prediction model for the presence of concomitant colorectal adenomas at the time of rectal biopsy. They also observed strong correlations between smoking status and rectal methylation pattern and between smoking status and the presence or risk of concomitant adenomas.

CONCLUSIONS

A prediction model was developed for the presence of colorectal adenomas based on gene methylation patterns in the normal rectum. The results indicated that these genes may be involved in early stages of adenoma formation. The observed epigenetic alterations in these markers may be caused in part by the effects of smoking and/or age. Normal rectal methylation may be useful as a biomarker for narrowing the population in need of screening colonoscopy.

Modifiable risk factors for colorectal neoplasms and hyperplastic polyps

PURPOSE

Obesity, smoking and alcohol are modifiable putative risk factors for colorectal neoplasms (CRN) and hyperplastic polyps (HP). The aim of this study was to evaluate the strength of association between these modifiable risk factors and colorectal polyps.

METHODS

These risk factors were assessed by using a questionnaire completed by the patient prior to colonoscopy. Eight hundred-seventy consecutive patients satisfying inclusion criteria who had undergone a complete colonoscopy were divided into 4 groups: CRN (n=194), HP (n=132), CRN and HP (n=42) and control (neither CRN nor HP; n=586). Multiple logistic regression was performed.

RESULTS

The ORs [95%CI] of both CRN and HP for incremental body mass index expressed in 2 categories (>or=22, >or=25) were 2.12 [1.00, 4.50] and 1.41 [0.53, 3.77], respectively. The ORs [95%CI] of CRN and HP for heavy smoking of over 20 pack-years were 1.66 [1.05, 2.64] and 1.67 [1.01, 2.77], respectively. The ORs of CRN and HP for habitual alcohol drinking (median ethanol intake 32 g/day and interquartile range 18-40 g/day) were 1.31 [0.86, 1.98] and 1.91 [1.06, 3.47], respectively. CRN and HP were correlated with each other (p=0.0043, chi-square test). Aging was a significant risk factor for all three groups of colorectal polyps.

CONCLUSION

These findings are especially important since smoking and alcohol consumption are modifiable risk factors. Heavy smokers should be encouraged to quit to reduce their risk of CRN and HP. Habitual drinkers should be warned of the risk of HP. HP can be a marker of coincidence of CRN.

Anthropometric risk factors for colorectal polyps in African-American women

OBJECTIVE

Colorectal adenomas are thought to be precursor lesions to colorectal cancer, a leading cause of cancer incidence and mortality in African-American women. Studies suggest that obesity is associated with risk of adenomas in white women, but little is known about the relation in African-American women. We prospectively examined the association between selected anthropometric factors and colorectal polyps in African-American women.

METHODS AND PROCEDURES

Data were obtained from the Black Women's Health Study (BWHS), a prospective cohort study of African-American women. From 1997 to 2003, we followed 33,403 women aged > or =30 years with no prior diagnosis of cancer or polyps. Cox regression was used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for risk of polyps, with adjustment for potential confounders.

RESULTS

After 211,797 person-years of follow-up, 1,189 cases of colorectal polyps were reported. The IRR comparing women with a current BMI > or =35 to <25 kg/m(2) was 1.35 (95% CI = 1.12-1.62), after adjustment for covariates including waist-to-hip ratio (WHR). Women who gained > or =30 kg since age 18 were 1.76 times as likely as those who gained <5 kg to report polyps (95% CI = 1.33-2.33). The IRR comparing the highest (>or =0.87) to lowest (<0.71) quintiles of WHR was 1.26 (95% CI = 1.04-1.54), after adjustment for covariates including BMI. BMI at age 18, adult height, and waist circumference (BMI-adjusted) were not materially associated with risk. Results were similar among women with a recent endoscopy.

DISCUSSION

Weight gain and obesity in adulthood may increase the risk of colorectal polyps in African-American women.

XRCC1, XRCC3, and XPD polymorphisms as modifiers of the effect of smoking and alcohol on colorectal adenoma risk

Using a sigmoidoscopy-based case-control study (753 cases, 799 controls) in Los Angeles County, we investigated the potential modifier role in the effect of alcohol and smoking of single-nucleotide polymorphisms (SNP) in three DNA repair genes, XRCC1 (Arg194Trp and Arg399Gln), XRCC3 (Thr241Met), and XPD (Lys751Gln). We have previously reported an inverse association between the XRCC1 codon 399 SNP and adenoma risk among these subjects. We now report that subjects with the XPD Gln/Gln genotype were inversely associated with adenoma risk [odds ratio (OR), 0.7; 95% confidence interval (95% CI), 0.5-1.0] when compared with subjects with the Lys/Lys and Lys/Gln genotypes combined. This association differed between different ethnic groups (gene x race heterogeneity likelihood ratio test, P = 0.009), with a stronger inverse association among Latinos (OR, 0.1; 95% CI, 0.01-0.5) than among non-Latinos (OR, 0.9; 95% CI, 0.-1.3). We found no evidence of an XRCC3 x smoking or alcohol interaction or an XRCC1 x alcohol interaction. Instead, our data supported an XRCC1 x smoking interaction (P = 0.048). Whereas XPD did not modify the effect of smoking, our data suggested an XPD x alcohol interaction. Analyses ignoring XPD showed no association between alcohol intake and adenoma prevalence; however, among carriers of the codon 751 Gln/Gln genotype, we found a significant positive association (OR, 2.5; 95% CI, 1.2-5.2 for ever drinkers; test of interaction P = 0.04). Our data suggest that the effects of smoking and alcohol may vary depending on the genetic background of proteins that participate in the base excision repair and nucleotide excision repair pathways.

Lifestyle-related risk factors and chemoprevention for colorectal neoplasia: experience from the large-scale NORCCAP screening trial

The objective of this study was to evaluate the potential beneficial effects of non-steroidal anti-inflammatory drugs (NSAIDs) and/or acetylsalicylic acid (ASA) and hormone replacement therapy (HRT) on colorectal neoplasia, and to compare their effects with those of lifestyle-related risk factors in 12 960 individuals who underwent flexible sigmoidoscopy screening examination. The association between these factors and colonic neoplasia was assessed by logistic regression analysis. NSAIDs and/or ASA intake were associated with decreased risk of distal low grade adenoma (DLGA) (adjusted odds ratio (OR) 0.80, P trend=0.02) in men. The duration of HRT was inversely related to the risk of DLGA (OR 0.89, P trend=0.08). Current smoking increased the risk of DLGA and distal advanced neoplasia (DAN) in both men (OR 2.50, P<0.01) and women (OR 2.30, P<0.01). There was a significant positive trend for increasing risk of DLGA (OR 1.16, P<0.01) and DAN (OR 1.20, P=0.02) with increasing use of alcohol among men, but not among women. Prescription of NSAIDs and/or ASA for chronic conditions may not be expected to have a substantial preventive effect on colorectal neoplasia in comparison with the adverse effect of smoking and alcohol. This may be explained by an increased risk of colorectal neoplasia for patients with conditions for which NSAIDs or ASA are being prescribed.

Dietary patterns and the risk of colorectal adenoma recurrence in a European intervention trial

The relations between individual foods and nutrients to colorectal tumours are conflicting. Few studies have taken into account the interdependence between individual components of diet and their possible interactions. The aim of the study was to examine the associations between dietary patterns and the risk of colorectal adenoma recurrence in the European fibre-calcium intervention trial. Among the 640 patients with confirmed adenomas at the index colonoscopy, 592 had an initial dietary assessment using a diet history questionnaire. The present analysis was restricted to 277 men and 165 women without history of adenoma prior to the index colonoscopy and who completed the study. The main end point was the 3-year recurrence of adenomas. Principal component analysis was used to identify dietary patterns from 50 food groups. Ninety-two patients presented new colorectal adenomas at the 3-year colonoscopy (65 men and 27 women). In men, three meaningful dietary patterns emerged from analysis, explaining 21.3% of variability. They were called 'Mediterranean', 'Sweets and snacks' and 'High fat and proteins' patterns. None of them were significantly related to the overall recurrence of colorectal adenomas either in univariate or multivariate analyses. Among women, the 'Mediterranean', the 'Western' and the 'Snacks' patterns explained 21.9% of variability. The 'Mediterranean' pattern characterized by a high consumption of olive oil, vegetables, fruit, fish and lean meat significantly reduced adenoma recurrence [second tertile: adjusted odds ratio (OR)=0.50, 95% confidence interval (CI)=0.18-1.42; third tertile: adjusted OR=0.30, 95% CI=0.09-0.98; P for linear trend=0.04]. The 'Western' and 'Snacks' patterns were not associated with recurrence among women. In conclusion, this study suggests that the Mediterranean dietary pattern may reduce the recurrence of colorectal adenomas, at least in women. These exploratory results need to be confirmed by larger studies.

Relation of cigarette smoking and alcohol use to colorectal adenomas by subsite: the self-defense forces health study

While smoking has consistently been shown to be related to increased risk of colorectal adenomas, few studies have addressed the association between smoking and site-specific colorectal adenomas. The reported association between alcohol use and colorectal adenomas has been inconsistent. We evaluated risks of adenomas at the proximal colon, distal colon, and rectum in relation to cigarette smoking and alcohol use, and their interaction. Subjects were 754 cases with histologically proven colorectal adenomas and 1547 controls with normal colonoscopy among male officials of the Self-Defense Forces (SDF) undergoing total colonoscopy at two SDF hospitals. Statistical adjustment was made for hospital, rank, body mass index, physical activity, and either smoking or alcohol drinking. Cigarette smoking was significantly associated with an increased risk of adenomas, regardless of the location of the adenomas, but the increased risk associated with smoking was more pronounced for rectal adenomas. Alcohol use was associated with moderately increased risks of distal colon and rectal adenomas, but not of proximal colon adenomas. Cigarette smoking, but not alcohol drinking, was associated with greater increases in the risk of large adenomas and of multiple adenomas across the colorectum. There was no measurable interaction of cigarette smoking and alcohol drinking on colorectal adenomas. The findings corroborate an increased risk of colorectal adenomas associated with smoking and a weak association between alcohol use and colorectal adenomas. Further studies are needed to confirm whether smoking is more strongly related to rectal adenomas, large adenomas, or multiple adenomas.

Primary prevention of colorectal cancer: diet and drugs

Primary prevention of colonic adenomas and cancer through dietary interventions or chemoprevention has great appeal. This article discusses primary prevention goals and promising nutritional or chemopreventive strategies. There is substantial observational evidence that diets high in total calories and fat and or low in fruits and vegetables or total fiber as well as low levels of physical activity are related to the risk of colonic neoplasia. Similar observational data indicate that diets high in specific nutrients such as antioxidant vitamins or calcium may be protective. The article describes some of the newer chemopreventive agents and reviews the data linking diet and lifestyle to colorectal cancer risk, focusing on interventions that have also been studied in prospective clinical trials. Finally the evidence supporting the role of non-steroidal anti-inflammatory drugs for the chemoprevention of CRC is reviewed and the status of several other promising newer agents that are entering human trials is summarized.

Prevention and chemoprevention of colorectal neoplasms

Main purpose of the review is to analyse the impact of the current approaches for colorectal cancer prevention, including chemoprevention. Available evidence does not support the contention that a more appropriate diet can be of great help in the prevention of these neoplasms, either because the scientific evidence is poor and highly controversial, or because changes in diet are difficult to implement, at least in many Western countries. Similarly, a preventive approach based on the modification of lifestyle remains improbable, either in the short --or in the long period of time. Secondary prevention--i.e., the systematic removal of adenomatous polyps--can hardly be applied in the general population, with the exception of individuals at risk because members of families with Adenomatosis coli or Lynch syndrome, or affected by inflammatory bowel diseases. Finally, chemoprevention (i.e., the attempt to prevent tumour development through the administration of drugs or natural compounds that interfere with various phases of carcinogenesis) is still in its infancy Though attractive, this approach requires well-designed studies which should be carried out for years before being evaluated and interpreted; so far most of these investigations gave inconsistent or controversial results. In conclusion, both primary and secondary prevention of colorectal malignancies appear difficult to apply in the general population, and chemoprevention is still at the beginning of a (presumably] long story. The final impression is that notwithstanding the remarkable advancements made in the last two decades in colorectal cancer research, the practical application of these new concepts remains difficult.

Glucose intolerance, plasma insulin levels, and colon adenomas in Japanese men

Hyperinsulinemia may be related to colon carcinogenesis. Several studies have suggested that diabetes mellitus is related to increased risk of colon cancer. We examined cross-sectionally the relation of fasting plasma insulin levels and glucose tolerance status to colon adenomas. In a consecutive series of 951 men undergoing total colonoscopy for a health examination at the Japan Self Defense Forces Fukuoka Hospital from April 1998 to August 1999, we identified 233 cases of colon adenomas and 497 controls with normal colonoscopy. Glucose tolerance status was determined by a 75-g oral glucose tolerance test, and subjects were classified as normal, impaired glucose tolerance (IGT) or non-insulin dependent diabetes mellitus (NIDDM). Plasma insulin levels were measured after subjects had fasted overnight. Logistic regression analysis and analysis of covariance was used to control for age and obesity. While plasma insulin levels were unrelated to colon adenomas, NIDDM was associated with a significantly increased risk of colon adenomas. There was no association between IGT and colon adenomas. NIDDM was more strongly associated with proximal colon adenomas. The findings suggest that long-term hyperinsulinemic status associated with NIDDM may increase the risk of colon adenomas, and subsequently of colon cancer.

Diet and colorectal adenoma in Japanese males and females

PURPOSE

The purpose of this study was to assess the relationship between risk of colorectal adenoma and dietary intake of nutrients and foods.

METHODS

In 1992, diet was assessed by a semiquantitative food-frequency questionnaire in a cohort of the Takayama Study in Japan. Patients were 181 male and 98 female cohort members who were newly histologically proved to have colorectal adenoma at colonoscopic examination between January 1, 1993, and December 31, 1995. Controls were 12,607 males and 15,754 females who had no history of colorectal polyp, adenoma, and cancer at baseline (1992) and were not diagnosed to have these diseases during the follow-up period.

RESULTS

In males, the risk of adenoma was significantly associated with intake of animal protein and vitamin A (relative risk, 1.42; 95 percent confidence interval, 1.00-2.04; and relative risk, 1.51; 95 percent confidence interval, 1.04-2.20, for the highest vs. lowest tertiles, respectively; P for trend = 0.048 and 0.03, respectively) after controlling for age, years of smoking, and alcohol intake. A significantly inverse association was observed for carbohydrate intake after controlling for the covariates (relative risk, 0.52; 95 percent confidence interval, 0.32-0.82, for the highest vs. lowest tertiles; P for trend = 0.02). Intakes of animal fat and cholesterol were marginally associated with risk of adenoma.

CONCLUSION

Some dietary components such as animal protein and carbohydrate, which have been associated with risk of colorectal adenoma or cancer in western populations, were also associated with risk of colorectal adenoma in the Japanese population.

Cigarette smoking and risk of bladder, pancreas, kidney, and colorectal cancers in Iowa

PURPOSE

Although there are numerous reports on the effects of cigarette smoking and cancer, they have infrequently compared risks at more than one cancer site after multivariate adjustment. We analyzed data from a population-based case-control study that included five anatomic sites to evaluate the association between cigarette smoking and each cancer site and to rank the associations by site.

METHODS

Study respondents included 1452 bladder, 406 kidney, 376 pancreatic, 685 colon, and 655 rectal cancer cases, as well as 2434 population controls. A self-administered questionnaire was used to collect information on cigarette smoking and other potential confounders including occupation, drinking water source, and dietary practices. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs), after adjustment for age, total energy intake, and other site- and sex-specific confounders.

RESULTS

In both sexes, cigarette smoking (ever vs. never) was associated with risk of bladder cancer (OR = 2.5; 95% CI, 2.0-3.1 for males; OR = 2.7; 2.0-3.6 for females) and pancreatic cancer (OR = 1.8; 1.2-2.8 for males; OR = 2.1; 1.4-3.1 for females). Cigarette smoking also increased the risk of kidney cancer among males (OR = 1.8; 1.3-2.7), and to a lesser degree, among females (OR = 1.2; 0.8-1.8). No association was found for colon or rectal cancer in either sex.

CONCLUSIONS

Cigarette smoking increased the risk of bladder, kidney, and pancreatic cancer in men and women. The rankings of multivariate-adjusted ORs from highest to lowest were bladder, pancreas, kidney, and colorectum, with little difference between men and women.

Colorectal cancer: molecules and populations

The epidemiology and molecular biology of colorectal cancer are reviewed with a view to understanding their interrelationship. Risk factors for colorectal neoplasia include a positive family history, meat consumption, smoking, and alcohol consumption. Important inverse associations exist with vegetables, nonsteroidal anti-inflammatory drugs (NSAIDs), hormone replacement therapy, and physical activity. There are several molecular pathways to colorectal cancer, especially the APC (adenomatous polyposis coli)-beta-catenin-Tcf (T-cell factor; a transcriptional activator) pathway and the pathway involving abnormalities of DNA mismatch repair. These are important, both in inherited syndromes (familial adenomatous polyposis [FAP] and hereditary nonpolyposis colorectal cancer [HNPCC], respectively) and in sporadic cancers. Other less well defined pathways exist. Expression of key genes in any of these pathways may be lost by inherited or acquired mutation or by hypermethylation. The roles of several of the environmental exposures in the molecular pathways either are established (e.g., inhibition of cyclooxygenase-2 by NSAIDs) or are suggested (e.g., meat and tobacco smoke as sources of specific blood-borne carcinogens; vegetables as a source of folate, antioxidants, and inducers of detoxifying enzymes). The roles of other factors (e.g., physical activity) remain obscure even when the epidemiology is quite consistent. There is also evidence that some metabolic pathways, e.g., those involving folate and heterocyclic amines, may be modified by polymorphisms in relevant genes, e.g., MTHFR (methylenetetrahydrofolate reductase) and NAT1 (N-acetyltransferase 1) and NAT2. There is at least some evidence that the general host metabolic state can provide a milieu that enhances or reduces the likelihood of cancer progression. Understanding the roles of environmental exposures and host susceptibilities in molecular pathways has implications for screening, treatment, surveillance, and prevention.

Cigarette smoking, alcohol use, and colorectal adenoma in Japanese men and women

PURPOSE

The aim of this study was to examine the relationships between smoking and alcohol use and risk of colorectal adenoma.

METHODS

Information about smoking, alcohol use, and other lifestyle variables were obtained prospectively from 14,427 male and 17,125 female residents in a city of Gifu Prefecture, Japan, by a self-administered questionnaire in September, 1992. Colorectal adenomas were newly diagnosed in 181 men and 78 women in this cohort between January, 1993 and December, 1995 by colonoscopic examination at two major hospitals of the city. Gender-specific and site-specific relative risks and 95 percent confidence intervals adjusted for age and for age plus other potential confounding factors were calculated by using logistic regression models.

RESULTS

Thirty or more years of smoking was significantly associated with risk of adenoma in general compared with never having smoked in both men and women (relative risk, 1.60; 95 percent confidence interval, 1.02-2.62 and relative risk, 4.54; 95 percent confidence interval, 2.04-9.08, respectively). Effect of smoking was stronger in the proximal colon. After adjusting for age and carbohydrate intake, total alcohol intake was not associated with risk of adenoma in any site in the colon in men. Sake drinkers were at significantly increased risk of adenoma in general, but the dose-response relationship was not statistically significant. Risk of adenoma in the rectum was not significantly increased for those who consumed >30.3 g/day of ethanol (relative risk, 5.7).

CONCLUSION

These data suggest that smoking is a risk factor of adenoma in Japanese men and women. The role of alcohol, however, is less clear.

MTHFR polymorphism, methyl-replete diets and the risk of colorectal carcinoma and adenoma among U.S. men and women: an example of gene-environment interactions in colorectal tumorigenesis

Our studies on interactions of a folate-metabolizing gene polymorphism and dietary intake in colorectal tumorigenesis demonstrate the potential importance of studying interactions between genotype and environmental exposure in relation to cancer risk. We observed an inverse association of a polymorphism (667C --> T, ala --> val) in the methylenetetrahydrofolate reductase (MTHFR) gene with colorectal cancer but not with colorectal adenomas. The inverse association of methionine and adverse association of alcohol with colorectal cancer were stronger among val/val individuals. These interactions were not present in studies of colorectal adenomas. Our studies illustrate that studying gene-environment interactions in relation to cancer can be of importance in clarifying cancer etiology as well as pointing to preventive dietary modifications.

Diet and lifestyle in the prevention of colorectal cancer: an overview

Numerous lifestyle factors have been implicated in colorectal carcinogenesis. These include diet, inadequate physical activity, obesity, alcohol consumption, and smoking. Epidemiologic studies, animal experiments, and randomized clinical trials have shown that dietary factors can influence all stages of colorectal carcinogenesis, from cell proliferation to transformation to cancer. Defining the precise role of diet and other lifestyle factors in colorectal carcinogenesis may require the elucidation of genetic susceptibility and genetic-environmental interactions. Despite the preoccupation with nutrition by the public and the media in the United States, trends in food consumption have not been favorable. The average U.S. diet is still too high in calories and fat and too low in fiber, cereals, fruits, and vegetables. Dietary modifications along with secondary prevention measures may have a major impact on reducing the mortality from colorectal cancer.

Risk factors for self-reported colon polyps

OBJECTIVE

Investigate risk factors for colon polyp using multivariate analyses.

DESIGN

In a group responding to a 1992 mail survey, we assessed the association between physician-diagnosed colon polyp and possible risk factors reported primarily 10 years earlier.

SETTING

Survey respondents within the Cancer Prevention Study II.

PARTICIPANTS

Respondents, 72,868 men and 81,356 women, who reported no polyp diagnosis when questioned in 1982 at ages 40 to 64 years.

MEASUREMENTS AND MAIN RESULTS

The characteristics of 7,504 men (10.3%) and 5,111 women (6.3%) reporting a first colon polyp were compared with those of participants who did not report a polyp. After adjustments for age, family history of colorectal cancer, and other potential risk factors, polyp occurrence was associated with 1982 histories of smoking, former smoking, alcohol use of at least two drinks per day (odds ratios [ORs] from 1.5 to 1.1; all p < .005), and a body mass index > or = 28 kg/m2 (men's OR 1.06; 95% confidence interval [CI] 1.00, 1.13; women's OR 1.08; 95% CI 0.99, 1.17). Polyps were also associated with a diagnosis of gallbladder disease or gallstone at any time and with gallbladder surgery up to 1982 (OR from 2.7 to 1.3; all p < .001). Polyp occurrence was inversely associated with 1982 histories of high exercise level (men's OR 0.83; 95% CI 0.76, 0.91; women's OR 0.90; 95% CI 0.78, 1.03), frequent aspirin use in women (OR 0.85; 95% CI 0.77, 0.95), and high parity in women (OR 0.84; 95% CI 0.75, 0.94). Among participants lacking a clinically normal gallbladder, the polyp risks associated with smoking and high body mass index were reduced (p < .04 for interactions).

CONCLUSIONS

Despite the limitations and potential biases in these self-reported data, the risk factors described here may be useful for identifying persons at modestly increased risk of having a colon polyp. The effect-modifying role of gallbladder status deserves further investigation.

Folate intake, alcohol consumption, cigarette smoking, and risk of colorectal adenomas

BACKGROUND

Recent evidence suggests that folic acid (and derivatives) could contribute to the protective effect of fruits and vegetables against the risk of large-bowel cancer. Other evidence indicates that alcohol drinking and cigarette smoking may impair the biologic actions of folate. We used data from an adenoma prevention trial to investigate the occurrence of colorectal adenomas (possible precursors of colorectal cancer) in association with folate intake, alcohol consumption, and cigarette smoking.

METHODS

Patients with at least one recent large-bowel adenoma were followed with colonoscopy 1 year and 4 years after their qualifying colon examinations. Adenomas detected after the year 1 examination were used as end points. A food-frequency questionnaire was administered at study entry and at study completion; nutrient intake at study entry was used in this analysis. All statistical tests were two-sided.

RESULTS

After adjustment for caloric intake, dietary folate had a significant protective association with the risk of recurrence of large-bowel adenoma (P for trend = .04). However, this inverse association was attenuated by further adjustment for intake of dietary fiber and fat. Use of folate supplements was not associated with a reduction in risk. Alcohol intake (seven or more drinks/week) was associated with increased risk (odds ratio = 2.04; 95% confidence interval = 1.28-3.26). Cigarette smoking, even smoking for long duration, was not related to adenoma recurrence.

CONCLUSIONS

These data provide only modest support for previous findings suggesting beneficial effects of folate on colorectal adenoma risk. We find no evidence that cigarette smoking increases risk. These findings do suggest a substantial increase in risk with alcohol consumption.

Epidemiology and risk factors for colorectal cancer

The striking geographic differences in colorectal cancer incidence and the changes in disease risk among immigrants suggest an important environmental component to colorectal cancer risk. Table 1 lists risk factors for colorectal cancer. The categories in the table are somewhat arbitrary but are designed to provide an overall semiquantitative summary of the current epidemiologic literature. Certain of the most important risk factors (e.g., age, family history) cannot be modified. Individuals at high risk might benefit from surveillance. Dietary factors appear to be among the most important determinants of colorectal cancer risk. Diet helps to explain geographic variation in disease. A diet that is high in red meat and saturated fat appears to increase risk. Vegetables, fruits, fiber, folate, and calcium may be protective. Obesity, particularly abdominal obesity, and tall stature may be risk factors. Physical activity has been repeatedly shown to reduce the risk of colorectal cancer. Postmenopausal hormone replacement therapy may also be protective. Exciting new data suggest a significantly lower risk of colorectal cancer in regular users of aspirin and NSAIDs. It is important to recognize that the use of these drugs can have adverse as well as beneficial effects, and the appropriate dose and timing are not known. Enough information is available to make recommendations to lower the risk of colorectal cancer. Reducing red meat and fat consumption; increasing fruits, vegetables, and grains; avoiding obesity; and adopting a regular program of physical activity reduce the risk of colorectal cancer. Fortunately, these modifications also decrease the risk of cardiovascular disease, an even more important cause of mortality in Western societies.

The relationship between smoking exposure and p53 overexpression in colorectal cancer

Although epidemiological studies of the relationship between cigarette smoking and colorectal cancer risk have been equivocal, a positive association is consistently found for colorectal adenoma development. We performed an epidemiological study to determine whether p53 protein overexpression, in tumours obtained at the time of resection, is associated with cigarette exposure in colorectal cancer. A total of 163 colorectal cancer cases and 326 healthy controls responded to a standardised questionnaire on colorectal cancer risk factors including detailed information on their history of cigarette smoking. All patients' tumours were analysed immunohistochemically for p53 overexpression using an avidin-biotin immunoperoxidase procedure and polyclonal anti-p53 antibody CM1. Comparison of colorectal cases with controls revealed an elevated risk for ex-smokers (OR = 1.34, 95% CI 0.85-2.12) and current smokers (OR = 1.13, 95% CI 0.63-2.02) when compared with non-smokers. No dose-response relationship was found for total pack-years of smoking (trend test: P = 0.19). However, a trend for total pack-years of smoking was found when p53-positive cases were compared with p53-negative cases suggesting aetiological, heterogeneity (trend test: P = 0.06). Estimating the individual relative risk of developing a p53-positive tumour relative to controls showed no associations for smoking status or total pack-years of smoking. However, when p53-negative cases were compared with controls, an elevated risk was found for ex-smokers (OR = 1.84, 95% CI 1.00-3.37) and current years of smoking (trend test: P = 0.03). Colorectal tumours developing through p53-positive dependent pathways were not associated with smoking exposure. A significant increase in risk was observed for the p53-negative independent pathway with smoking. p53 overexpression appears to be associated with smoking exposure in colorectal cancer.

Physical activity, obesity, and risk of colorectal adenoma in women (United States)

The relationship between physical inactivity, body mass index (BMI) (wt[kg]/ht[m]2), and pattern of adipose distribution with risk of colorectal adenomas (precursors of cancer) was examined in 13,057 female nurses in the United States, 40 to 65 years of age in 1986, who had an endoscopy between 1986 and 1992. From 1986 to 1992, 439 participants were newly diagnosed with adenomas of the distal colorectum. After controlling for age, prior endoscopy, parental history of colorectal cancer, smoking, aspirin, and intakes of animal fat, dietary fiber, folate, methionine, and alcohol, physical activity was associated inversely with risk of large (> or = 1 cm) adenomas in the distal colon (relative risk [RR] = 0.57, 95 percent confidence interval [CI] = 0.30-1.08, comparing high and low quintiles of average weekly energy expenditure from leisure-time activities; P trend = 0.05). Much of the benefit came from activities of moderate intensity such as brisk walking. In addition, BMI was associated directly with risk of large adenomas in the distal colon (multivariate RR = 2.21 [CI = 1.18-4.16], P trend = 0.0001, for BMI > or = 29 cf < 21 kg/m2). Waist circumference and the waist-to-hip ratio (WHR) were not related significantly to adenoma independently of BMI, but women with both a high BMI and high WHR were at greater risk of large colon adenoma (multivariate RR = 1.99, CI = 0.98-4.05) than women with high BMI but relatively low WHR (multivariate RR = 1.35, CI = 0.61-2.97). BMI was not related to small (< 1 cm) adenoma risk but physical activity had an inverse association with small adenomas in the distal colon (multivariate RR = 0.68, CI = 0.40-1.15, P trend = 0.03). The relationships between BMI or physical activity were considerably weaker and inconsistent for rectal adenomas. These results, in women, support an inverse association between physical activity and occurrence or progression of adenomas in the distal colon; obesity is associated with an elevated risk of large adenomas.

Nutrition and colorectal cancer

Epidemiologic evidence on the relation between nutrition and colorectal cancer is reviewed. Colon cancer varies approximately 20-fold internationally. Although there is clear evidence of genetic predisposition to colon cancer, much of this variation appears to be related to differences in dietary habits. At present, the data suggest that vegetables are associated with lower risk, and that fiber alone does not account for this association. Further, meat consumption is associated with increased risk but this, too, is not explained solely by its fat content. Several microconstituents of the diet may be associated with reduced risk--including folate and calcium--but phytochemicals of other sorts may be relevant. Mutagenic compounds, particularly heterocyclic amines, produced when protein is cooked, plausibly explain the meat association. The most consistent inverse association is with physical activity. Alcohol is associated, though inconsistently, with increased risk. Rectal cancer is less well studied but, at present, there are few data to suggest that the dietary risk factors are markedly different. Physical activity does not appear to be associated with a lower risk. Colorectal adenomatous polyps also appear to share the spectrum of risk factors seen with colon cancer, although, for adenomas, tobacco smoking is also a clear and consistent risk factor. There are a variety of links between the dietary epidemiology and physiology of colorectal neoplasia and the relevant pathologic and molecular changes. Other causal connections remain to be explicated.

Relationship of cigarette smoking, alcohol use, and dietary habits with sigmoid colon adenomas

The relationship between cigarette smoking, alcohol use, and dietary factors and the risk of adenomas of the sigmoid colon was examined in male self-defense officials who received a preretirement health examination at three Self-Defense Forces hospitals in Japan. In the comparison between 228 patients with sigmoid adenomas and 1484 control subjects with normal colonoscopy findings (> or = 60 cm from the anus), a clear dose-response relationship was observed between cigarette smoking and risk of adenoma. After adjustment for rank, body mass index, alcohol use, and physical activity as well as for hospital and survey season, the odds ratios (and 95% confidence intervals (CIs)) for the categories of 0, 1 to 399, 400 to 799, and 800 or more cigarette-years were 1.0, 2.1 (1.2 to 3.5), 2.8 (1.8 to 4.3), and 3.5 (2.1 to 5.8), respectively. Current alcohol drinkers tended to have an increased risk, but without a dose-response relation. Among four types of alcoholic beverages (shochu, sake, beer, and whiskey), only whiskey showed a weak association with risk of adenoma. None of the 13 dietary items studied (including meat and rice consumption) was measurably associated with adenoma risk. The present findings provide additional evidence that cigarette smoking is a risk factor for colon adenomas. It is inconclusive regarding alcohol intake's association with adenoma risk.

The relation of smoking, alcohol use and obesity to risk of sigmoid colon and rectal adenomas

We conducted a case-control study, using 429 cases with histologically confirmed sigmoid adenoma, 75 cases with rectal adenoma, and 3101 controls showing normal colonoscopy at least up to 60 cm from the anus. The subjects were male Self-Defense Forces personnel aged 48-56 who received a retirement health examination including a routine sigmoid- or colonoscopy. Lifestyle characteristics were ascertained by a self-administered questionnaire. Smoking in the recent past (< or = 10 years preceding the colonoscopy) and smoking in the remote past (> 10 years before the colonoscopy) were both significantly associated with risk of sigmoid adenoma but not with rectal adenoma as a whole. After reciprocal adjustment for smoking in the two periods, only smoking in the recent past was associated with both sigmoid colon and rectal adenomas. Odds ratios (OR) of sigmoid adenoma (and 95% confidence interval) for the categories of 0, 1-150, 151-250 and > or = 251 cigarette-years were 1.0 (reference), 1.9 (1.3-2.8), 2.1 (1.4-3.0) and 3.0 (1.9-4.7), respectively (P for trend < 0.01), and those for rectal adenoma were 1.0 (reference), 1.2 (0.4 3.2), 3.5 (1.4-8.5) and 2.0 (0.6 6.7), respectively (P for trend = 0.03). Alcohol use was significantly positively associated with sigmoid adenoma, and insignificantly associated with rectal adenoma. Body mass index was significantly positively associated with sigmoid adenoma, especially large ones. No such association was found for rectal adenoma. These findings suggest that smoking, especially in the recent past, and alcohol use are common risk factors for sigmoid colon and rectal adenomas while obesity may be exclusively related to the growth of sigmoid adenoma.

Dietary factors and risk of colon cancer

The incidence rates of colon cancer are high in North America and northern Europe, lower in southern Europe, and much lower in Asia and Africa. It is widely believed that environmental factors, particularly dietary patterns, account for most of this marked variation in rates. Over the past decade, a large number of case-control and cohort studies have added a substantial body of evidence regarding our understanding of the causes of colon cancer. Although the data are not entirely consistent, several important risk factors have emerged. The epidemiological evidence that physical inactivity or excess energy intake relative to requirements increases risk of this malignancy is quite strong. Intake of red meat appears to increase risk, but protein-rich sources other than red meat probably do not elevate risk and may even reduce the occurrence of colon cancer. Dietary fat, at least that from sources other than red meat, does not appear to increase risk appreciably. High consumption of vegetables and fruits and the avoidance of highly refined sugar containing foods are likely to reduce risk of colon cancer, although the responsible constituents remain unclear. Alcohol intake may enhance risk of cancers of the distal colorectum, although the evidence is not entirely consistent. The influence of alcohol may be particularly strong when combined with a diet low in methionine and folate, suggesting that the effect of alcohol may be through antagonism of methyl-group metabolism. The combined effect of these dietary factors, as well as modifiable non-dietary factors such as cigarette smoking, suggest that the majority of cases of colon cancer are preventable.

Cigarette smoking and other behavioral risk factors for recurrence of colorectal adenomatous polyps (New York City, NY, USA)

Adenomatous polyps (hereinafter referred to as adenomas) are known precursors of colorectal cancer. Cigarette smoking has been associated with adenomas but not with colorectal cancer, while alcohol and fat intake have been associated with both adenomas and cancer in some studies. Approximately 30 percent of patients with resected adenomas develop another adenoma within three years. This case-control study explores the association of cigarette smoking with adenoma recurrence. Between April 1986 and March 1988, we administered a questionnaire to colonoscoped patients aged 35 to 84 years in three New York City (NY, USA) practices. We compared 186 recurrent polyp cases (130 males, 56 females) and 330 controls (187 males, 143 females) who had a history of polypectomy but normal follow-up colonoscopy, by cigarette-smoking pack-years adjusted for possible confounders. Risk for a metachronous or recurrent adenoma was significantly greater in the highest quartile of smokers than in never-smokers among both men (odds ratio [OR] = 1.8, 95 percent confidence interval [CI] = 1.0-3.4) and women (OR = 3.6, CI = 1.7-7.6). Adjustment for time since smoking cessation reduced risk only slightly, as did adjustment for dietary fat intake, which itself remained significant. No association was found between alcohol intake and risk of recurrence. Cigarette smokers appear to have an elevated risk of adenoma recurrence that is not eliminated entirely by smoking cessation. Intervention trials that use adenoma recurrence as an endpoint should take smoking into account.

Obesity and adenomatous polyps of the sigmoid colon

The relation between obesity and adenomatous polyps of the sigmoid colon was investigated in male self-defense officials who received a retirement health examination at three hospitals of the Self-Defense Forces in Japan between January 1991 and December 1992. Body mass index (BMI) and waist-hip circumference ratio (WHR) were used as indices of obesity. A total of 228 adenoma cases and 1484 controls with normal sigmoidoscopy were identified in 2228 men: cases having small adenomas (< 5 mm in diameter) and those with large adenomas (5 mm or greater) numbered 115 and 102, respectively. Smoking, alcohol use, physical activity, rank, and hospital were controlled for by multiple logistic regression analysis. BMI and WHR were classified into four levels using the 30th, 60th, and 90th percentiles of each distribution in the control as cut-off points. There was a significant two-fold elevation in the overall adenoma risk among men at the highest BMI level (> or = 26.95) compared with those at the lowest level (< 22.48), but the risk did not linearly increase: a similar increase was also noted for large adenomas. While WHR was only weakly related to the overall adenoma risk, the risk of large adenomas progressively increased with increasing levels of WHR; odds ratio (OR) 2.9 (95% confidence interval (CI) 1.4-5.9) for the highest (> or = 0.958) versus lowest (< 0.878) levels. BMI was not materially associated with adenoma risk after additional adjustment for WHR, but a positive association between WHR and large adenomas was independent of BMI: OR 3.4 (95% CI 1.5-7.6) for the highest versus lowest levels. These findings suggest that obesity is associated with an increased risk of colon adenomas, probably with adenoma growth.