A sigmoidoscopy-based case-control study of polyps: macronutrients, fiber and meat consumption

Association between Dietary Fiber Intake and Colorectal Adenoma

Dietary fiber intake has been suggested to decrease the risks of colorectal cancer (CRC) and adenoma. This cross-sectional study aimed to evaluate the association between total dietary fiber intake and colorectal adenoma among asymptomatic Korean adults. Individuals who received a screening colonoscopy between May and December of 2011 were recruited. Multivariable-adjusted logistic regression was used to assess the odds ratios (ORs) and 95% confidence intervals (CIs) of colorectal adenoma. 558 of the 1,716 study participants were diagnosed with colorectal adenoma. No significant association between total dietary fiber intake and colorectal adenoma was found; ORs (95% CIs) for subsequent quintiles compared to the bottom quintile were 1.00 (0.69-1.46), 1.11 (0.73-1.71), 0.97 (0.57-1.65), and 0.88 (0.46-1.71; P for trend = 0.65). Dietary fiber intakes from cereal, fruit, vegetable, or legume weren't associated with colorectal adenoma. When we compared >30 g/d to ≤10 g/d of total dietary fiber intake, OR (95% CI) was 0.32 (0.10-1.02; P for trend = 0.23). In the analyses of advanced or high-risk state and location of adenoma, we didn't observe significant associations. In conclusion, dietary fiber intake was not associated with colorectal adenoma in Korean adults. However, the association for low intake of dietary fiber warrants further investigation.

Association between Dietary Fibre Intake and Colorectal Adenoma: A Systematic Review and Meta-Analysis

PubMed/Medline, Excerpta Medica dataBASE (EMBASE) and Scopus were searched in January 2021 in order to retrieve evidence assessing the association between dietary fibre intake and the risk of colorectal adenoma in adults. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for the reporting of results. Only primary observational studies were included. Publication bias was estimated through the Egger's test and the visual inspection of the funnel plot. Heterogeneity between studies was calculated with I2 statistics. The search strategy identified 683 papers, 21 of which were included in our meta-analysis. Having evaluated a total of 157,725 subjects, the results suggest a protective effect of dietary fibre intake against colorectal adenoma. Effect Size (ES) was [0.71 (95% CI = 0.68-0.75), p = 0.000)]. Moderate statistical heterogeneity (Chi2 = 61.68, df = 23, I2 = 62.71%, p = 0.000) was found. Findings show a statistically significant (p = 0.000) and robust association between a higher intake of dietary fibre and a lower risk of colorectal adenoma, considering both the prevalent and incident risk. Moreover, the meta-regression analysis showed a borderline significant negative linear correlation between the amount of dietary fibre intake and colorectal adenoma. Lastly, we performed a subgroup analysis by sex, showing a higher protective effect for men.

Different dietary fibre sources and risks of colorectal cancer and adenoma: a dose-response meta-analysis of prospective studies

Dietary fibre is believed to provide important health benefits including protection from colorectal cancer. However, the evidence on the relationships with different dietary fibre sources is mixed and little is known about which fibre source provides the greatest benefits. We conducted a dose-response meta-analysis of prospective cohorts to summarise the relationships of different fibre sources with colorectal cancer and adenoma risks. Analyses were restricted to publications that reported all fibre sources (cereals, vegetables, fruits, legumes) to increase comparability between results. PubMed and Embase were searched through August 2018 to identify relevant studies. The summary relative risks (RR) and 95 % CI were estimated using a random-effects model. This analysis included a total of ten prospective studies. The summary RR of colorectal cancer associated with each 10 g/d increase in fibre intake were 0·91 (95 % CI 0·82, 1·00; I2 = 0 %) for cereal fibre, 0·95 (95 % CI 0·87, 1·03, I2 = 0 %) for vegetable fibre, 0·91 (95 % CI 0·78, 1·06, I2 = 43 %) for fruit fibre and 0·84 (95 % CI 0·63, 1·13, I2 = 45 %) for legume fibre. For cereal fibre, the association with colorectal cancer risk remained statistically significant after adjustment for folate intake (RR 0·89, 95 % CI 0·80, 0·99, I2 = 2 %). For vegetable and fruit fibres, the dose-response curve suggested evidence of non-linearity. All fibre sources were inversely associated with incident adenoma (per 10 g/d increase: RR 0·81 (95 % CI 0·54, 1·21) cereals, 0·84 (95 % CI 0·71, 0·98) for vegetables, 0·78 (95 % CI 0·65, 0·93) for fruits) but not associated with recurrent adenoma. Our data suggest that, although all fibre sources may provide some benefits, the evidence for colorectal cancer prevention is strongest for fibre from cereals/grains.

Association between red and processed meat intake and colorectal adenoma incidence and recurrence: a systematic review and meta-analysis

The associations between red and processed meat intake and colorectal adenoma (CRA) incidence and recurrence are inconclusive. We performed a systematic review and meta-analysis to analysis these associations. We conducted a systematic search of PubMed, EMBASE and Web of Science up to December 2016. The relative risks (RRs) and 95% confidence intervals (CIs) were assessed. Subgroup analyses, dose-response-analyses, subtype analyses and analyses of CRA locations were also conducted. Twenty-seven studies that involved 208,117 participants and 19,150 cases met criteria. The RRs of the highest versus lowest intakes for CRA incidence were 1.23 (1.15–1.31) for red meat and 1.15 (1.07–1.24) for processed meat. Dose-response analyses for meat per 100 g/day yielded the results were consistent with the original analyses, with 1.14 (1.07–1.20) for red meat and 1.27 (1.03–1.50) for processed meat. Additionally, there were no associations between red and processed meat intake and CRA recurrence, including total CRA (P > 0.05), advanced CRA (P > 0.05) and multiple CRA (P > 0.05). In conclusion, our findings support the hypothesis that red and processed meat intake was associated with an increased CRA incidence but not for CRA recurrence.

Meat subtypes and their association with colorectal cancer: Systematic review and meta-analysis

Associations between specific red meat subtypes and risk of colorectal cancer (CRC) have been investigated in a number of epidemiological studies. However, no publication to date has summarised the overall epidemiological evidence. We conducted a systematic review and meta-analysis of prospective studies (cohort, nested case-control or case-cohort studies), which reported relative risk (RR) estimates and 95% confidence intervals (CI) for the association between intake of meat subtypes with colorectal, colon or rectal cancer or colorectal adenoma risk. PubMed and ISI Web of Science were searched up until August 1, 2014. Nineteen studies examined meat subtypes (5 beef, 5 pork, 2 lamb, 1 veal and 19 poultry) and associations with colorectal, colon or rectal cancer risk and 4 studies examined associations with adenoma risk (1 beef and 4 poultry). Comparing highest versus lowest intake, beef consumption was associated with an increased risk of CRC (RR = 1.11, 95% CI = 1.01 to 1.22) and colon cancer (RR = 1.24, 95% CI = 1.07 to 1.44), but no association was found with rectal cancer (RR = 0.95, 95% CI = 0.78 to 1.16). Higher consumption of lamb was also associated with increased risk of CRC (RR = 1.24, 95% CI = 1.08 to 1.44). No association was observed for pork (RR = 1.07, 95% CI = 0.90 to 1.27), but some between study heterogeneity was observed. No association was observed for poultry consumption and risk of colorectal adenomas or cancer. This meta-analysis suggests that red meat subtypes differ in their association with CRC and its sub sites. Further analysis of data from prospective cohort studies is warranted, especially regarding the role of pork.

Dietary fiber intake reduces risk for colorectal adenoma: a meta-analysis

BACKGROUND & AIMS

Reports on the association between dietary fiber intake and risk of colorectal adenoma (CRA), the precursor of colorectal cancer, have been inconsistent. We conducted a meta-analysis of case-control and cohort studies to analyze this association.

METHODS

We searched the MEDLINE and EMBASE databases to identify relevant studies published through July 2013. A random-effects model was used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs) for associations between fiber intake and CRA risk. Heterogeneity among studies was assessed using the Cochran Q and I(2) statistics.

RESULTS

Our meta-analysis included 20 studies involving 10,948 subjects with CRA. The SRRs of CRA for total dietary fiber were 0.72 (95% CI, 0.63-0.83) in a high- vs low-intake analysis and 0.91 (95% CI, 0.87-0.95) per 10-g/day increase in fiber intake in a dose-response model. Subgroup analyses indicated a significant inverse association between total fiber intake and CRA risk in case-control studies (SRR, 0.66; 95% CI, 0.56-0.77), but not in cohort studies (SRR, 0.92; 95% CI, 0.76-1.10). The SRRs of CRA were 0.84 for fruit fiber (95% CI, 0.76-0.94; n = 6 studies), 0.93 for vegetable fiber (95% CI, 0.84-1.04; n = 6 studies), and 0.76 for cereal fiber (95% CI, 0.62-0.92; n = 9 studies) in high- vs low-intake analyses.

CONCLUSIONS

Our findings support the hypothesis that high dietary fiber intake is associated inversely with CRA risk. Further studies with prospective designs that use validated questionnaires and control for important confounders are warranted.

Genetic variation in the base excision repair pathway, environmental risk factors, and colorectal adenoma risk

Cigarette smoking, high alcohol intake, and low dietary folate levels are risk factors for colorectal adenomas. Oxidative damage caused by these three factors can be repaired through the base excision repair pathway (BER). We hypothesized that genetic variation in BER might modify colorectal adenoma risk. In a sigmoidoscopy-based study, we examined associations between 182 haplotype tagging SNPs in 14 BER genes, and colorectal adenoma risk, and examined their potential role as modifiers of the effect cigarette smoking, alcohol intake, and dietary folate levels. Among all individuals, no statistically significant associations between BER SNPs and adenoma risk persisted after correction for multiple comparisons. However, among Asian-Pacific Islanders we observed two SNPs in FEN1 and one in NTHL1, and among African-Americans one SNP in APEX1 that were associated with colorectal adenoma risk. Significant associations were also observed between SNPs in the NEIL2 gene and rectal adenoma risk. Three SNPS modified the effect of smoking (MUTYH interaction p = 0.002; OGG1 interaction p = 0.013); FEN1 interaction p = 0.013)), one SNP in LIG3 modified the effect of alcohol consumption (interaction p = 0.024) and two SNPs in LIG3 modified the effect of dietary folate (interaction p = 0.001 and p = 0.08) on colorectal adenoma risk. These findings support a role for genetic variants in the BER pathway as potential modifiers of colorectal adenoma risk. Our findings strengthen the role of oxidative damage induced by key lifestyle and dietary risk factors in colorectal adenoma formation.

Red and processed meat intake and risk of colorectal adenomas: a systematic review and meta-analysis of epidemiological studies

BACKGROUND

Current evidence indicates that red and processed meat intake increases the risk of colorectal cancer; however, the association with colorectal adenomas is unclear.

OBJECTIVE

To conduct a systematic review and meta-analysis of epidemiological studies of red and processed meat intake and risk of colorectal adenomas as part of the Continuous Update Project of the World Cancer Research Fund.

DESIGN

PubMed and several other databases were searched for relevant studies from their inception up to 31 December 2011. Summary relative risks (RRs) were estimated using a random effects model.

RESULTS

Nineteen case-control studies and seven prospective studies were included in the analyses. The summary RR per 100 g/day of red meat was 1.27 (95 % CI 1.16-1.40, I (2) = 5 %, n = 16) for all studies combined, 1.20 (95 % CI 1.06-1.36, I (2) = 0 %, n = 6) for prospective studies, and 1.34 (95 % CI 1.12-1.59, I (2) = 31 %, n = 10) for case-control studies. The summary RR per 50 g/day of processed meat intake was 1.29 (95 % CI 1.10-1.53, I (2) = 27 %, n = 10) for all studies combined, 1.45 (95 % CI 1.10-1.90, I (2) = 0 %, n = 2) for prospective studies, and 1.23 (95 % CI 0.99-1.52, I (2) = 37 %, n = 8) for case-control studies. There was evidence of a nonlinear association between red meat (p nonlinearity < 0.001) and processed meat (p nonlinearity = 0.01) intake and colorectal adenoma risk.

CONCLUSION

These results indicate an elevated risk of colorectal adenomas with intake of red and processed meat, but further prospective studies are warranted.

Colorectal polyp type and the association with charred meat consumption, smoking, and microsomal epoxide hydrolase polymorphisms

We determined the association between charred meat consumption, cigarette smoking, microsomal epoxide hydrolase (mEH) polymorphisms (rs1051740 and rs2234922), and colorectal adenomas and hyperplastic polyps (HPs) and explored gene-environment interactions. Men and women with colorectal adenomas (n = 519), HPs (n = 691), or concurrently with both types of polyps (n = 227) and polyp-free controls (n = 772) receiving a colonoscopy from December 2004 to September 2007 were recruited. Participants completed telephone interviews and provided buccal cell samples; genotyping of mEH was completed using Taqman assays. We conducted polytomous regression and calculated odd ratios (OR) and 95% confidence intervals. Interactions were evaluated using Wald chi-square tests. Consumption of >3 servings of charred meat per week was associated with distal HPs (OR = 2.0, 1.2-3.4) but not adenomas nor either type of proximal polyp. Heavy cigarette smoking (≥ 22 pack-years) was associated with an increased risk for colorectal adenomas (OR = 1.7, 95% CI: 1.2-2.4), HPs (OR = 2.4, 95% CI: 1.7-3.3), and both types (OR = 2.8, 95% CI: 1.8-4.3) with the strongest association for distal polyps. There was no association between mEH genotype and colorectal polyps, nor were any statistically significant gene-environment interactions identified. Future investigation of BaP exposure and colorectal neoplasia should analyze whether associations are dependent upon anatomic location.

Hematopoietic prostaglandin D synthase (HPGDS): a high stability, Val187Ile isoenzyme common among African Americans and its relationship to risk for colorectal cancer

Intestinal tumors in Apc(Min/+) mice are suppressed by over-production of HPGDS, which is a glutathione transferase that forms prostaglandin D(2) (PGD(2)). We characterized naturally occurring HPGDS isoenzymes, to see if HPGDS variation is associated with human colorectal cancer risk. We used DNA heteroduplex analysis and sequencing to identify HPGDS variants among healthy individuals. HPGDS isoenzymes were produced in bacteria, and their catalytic activities were tested. To determine in vivo effects, we conducted pooled case-control analyses to assess whether there is an association of the isoenzyme with colorectal cancer. Roughly 8% of African Americans and 2% of Caucasians had a highly stable Val187lle isoenzyme (with isoleucine instead of valine at position 187). At 37°C, the wild-type enzyme lost 15% of its activity in 1h, whereas the Val187Ile form remained >95% active. At 50°C, the half life of native HPGDS was 9min, compared to 42 min for Val187Ile. The odds ratio for colorectal cancer among African Americans with Val187Ile was 1.10 (95% CI, 0.75-1.62; 533 cases, 795 controls). Thus, the Val187Ile HPGDS isoenzyme common among African Americans is not associated with colorectal cancer risk. Other approaches will be needed to establish a role for HPGDS in occurrence of human intestinal tumors, as indicated by a mouse model.

Dietary fatty acids and recurrence of colorectal adenomas in a European intervention trial

Epidemiological studies have provided inconsistent data about the role of dietary fatty acids in colorectal cancer, and few studies have addressed their role in colorectal adenoma. The aim of the study was to assess the risk of overall adenoma recurrence associated with dietary consumption of total fat, subtypes of fat, and specific fatty acids (oleic acid, linoleic acid, alpha-linolenic acid). The study sample was composed of 523 patients with confirmed adenomas at the index colonoscopy, 35 to 75 yr old, who completed the European fiber-calcium intervention trial and had an initial dietary assessment using a qualitative and quantitative food questionnaire. The overall 3-yr recurrence rate was 22.6% (118 out of 523 patients). There were no significant associations between overall adenoma recurrence and either total fat, subtypes of fat, or specific fatty acids. However, polyunsaturated fatty acids and linoleic acid were both moderately but significantly associated with distal and multiple recurrence. No significant associations were observed with recurrence of proximal or advanced adenomas. Our findings do not support the hypothesis of strong associations between dietary fatty acids and recurrence of colorectal adenomas. The hypothesis of a differential role of specific fatty acids according to colorectal subsites deserves further investigation.

Marine n-3 and saturated fatty acids in relation to risk of colorectal cancer in Singapore Chinese: a prospective study

Experimental data support multiple roles for fatty acids in colorectal carcinogenesis. We examined dietary fatty acids and incidence of colorectal cancer, and evaluated effect modification by sex and stage of disease among a population-based cohort of 61,321 Singapore Chinese that was established between 1993 and 1998. As of December 31, 2005, 961 incident colorectal cancers were diagnosed. Presented hazard ratios (HRs) are for highest versus lowest quartiles with adjustment for potential confounders. Among women, we observed a dose-dependent, positive association between saturated fat and localized colorectal cancer (Dukes A or B) [(HR=1.69, 95% confidence interval (CI)=1.08-2.63, p for trend=0.01)]. No such associations were noted in men (p for interaction by sex=0.04). Marine n-3 polyunsaturated fatty acid (PUFA) intake was positively associated with advanced disease (Dukes C or D) (HR=1.33, 95% CI=1.05-1.70, p for trend=0.01), regardless of sex. The association with marine n-3 PUFAs was strongest among those with the shortest (<or=5 years) duration of follow-up (HR=1.49, 95% CI=1.00-2.21, p for trend=0.04). In contrast, we observed a small, albeit imprecise, inverse association with marine n-3 PUFAs for localized colorectal cancer among those with the longest duration of follow-up (>10 years) (HR=0.62, 95% CI=0.29-1.34, p for trend=0.55). Our findings suggest that subtypes of fatty acids may differentially influence risk of colorectal cancer of a specified stage.

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.

Modeling exposures for DNA methylation profiles

We extend the finite mixture model to estimate the association between exposure and latent disease subtype measured by DNA methylation profiles. Estimates from this model are compared with those obtained from the simpler two-phase approach of first clustering the DNA methylation data followed by associating exposure with disease subtype using logistic regression. The two models are fit to data from a study of colorectal adenomas and are compared in a simulation study. Depending on the analytic approach, we obtain different estimates of the odds ratio (OR) and its 95% confidence interval (95% CI) for the association of RBC folate and DNA methylation subtype in colorectal adenomas (OR, 0.31; 95% CI, 0.08-1.26 from the extended finite mixture model; OR, 0.44; 95% CI, 0.15-1.28 from the two-phase approach; n = 58 case subjects). Although our results could be a chance occurrence due to fluctuations from small sample size, we did a simulation study using larger samples and found that differences between the two approaches emerge when there is noise in the cluster analysis. In the naive two-phase approach, the estimate of the OR is biased towards the null, and its SE is underestimated when there is error in the cluster assignment. Estimates from the extended mixture model are unbiased and have the correct SE estimate but may require larger sample sizes for convergence. Thus, when the clusters are not identified with certainty, the extended mixture model is preferred for valid estimation of the OR and CI.

XRCC1 and XRCC3 polymorphisms and their role as effect modifiers of unsaturated fatty acids and antioxidant intake on colorectal adenomas risk

Whereas animal and in vitro studies support a role of unsaturated fatty acids in colon carcinogenesis, the epidemiologic evidence is inconclusive. Using a large sigmoidoscopy-based case-control study (753 cases and 799 controls) in Los Angeles County, we investigated possible associations between single-nucleotide polymorphisms in the XRCC1 (codons 194 Arg/Trp and codon 399 Arg/Gln) and XRCC3 (codon 241 Thr/Met) genes and colorectal adenoma risk and their possible role as modifiers of the effect of monounsaturated fatty acid, the ratio of omega-6/omega-3 polyunsaturated fatty acids, and antioxidant intake. We found no evidence of associations between the XRCC1 codon 194 Arg/Trp or Trp/Trp genotypes and the XRCC3 codon 241 Thr/Met or Met/Met genotypes. Subjects with the XRCC1 Gln/Gln genotype were inversely associated with adenoma risk (odds ratio, 0.6; 95% confidence interval, 0.4-0.9; P = 0.01) when compared with subjects with Arg/Arg and Arg/Gln genotypes combined. We found no evidence of gene-dietary fat interactions for the XRCC3 codon 241 polymorphism. However, our data suggest an XRCC1-unsaturated fat interaction. High monounsaturated fatty acid intake was associated with adenoma risk only among subjects with the XRCC1 codon 194 Arg/Arg and codon 399 Gln/Gln combined genotypes (P for interaction = 0.018). High omega-6/omega-3 polyunsaturated fatty acid ratios were associated with adenoma risk among subjects with the XRCC1 codon 194 Arg/Arg and codon 399 Gln/Gln or the codon 194 Arg/Trp or Trp/Trp and codon 399 Arg/Arg or Arg/Gln combined genotypes (P for interaction = 0.026). These interactions were not modified by antioxidant intake. However, low antioxidant intake was associated with an inverse association only among subjects with the XRCC1 codon 194 Arg/Trp or Trp/Trp and codon 399 Arg/Arg or Arg/Gln combined genotypes (P for interaction = 0.022), which was independent of unsaturated fat intake. Our data suggest that the XRCC1 codon 194 and codon 399 single nucleotide polymorphisms may modify the effect of unsaturated fatty acid and antioxidant intake and that this XRCC1 effect modification may explain, in part, previously reported inconsistencies on the role of unsaturated fatty acids and adenoma risk.

A molecular/epidemiologic analysis of expression of cyclooxygenases 1 and 2, use of nonsteroidal antiinflammatory drugs, and risk of colorectal adenoma

Nonsteroidal antiinflammatory drugs (NSAIDs) are postulated to protect against colorectal cancer and adenomas at least in part by a cyclooxygenase (COX-mediated mechanism. The results reported herein address the questions of what factors are associated with expression (relative messenger RNA levels) of COX-1 and COX-2 in colorectal adenomas and whether there is heterogeneity in the protective effect of NSAIDs by levels of COX expression. Paraffin-embedded tissue samples and data describing selected risk factors were obtained from cases enrolled in a case-control study of colorectal adenomatous polyps. RNA was isolated from paraffin-embedded specimens. Samples of complementary DNA were quantified using a fluorescence-based real-time detection method. We tested for differences in levels of COX expression among selected subgroups of cases using a standard Student t test. Odds ratios for the effects of NSAID variables were calculated using unconditional logistic regression in order to make use of all available data on COX expression. Results suggest that use of NSAIDs is associated with lower levels of COX-2 expression and that the protective effect of NSAIDs on polyp occurrence is stronger in the subgroup of cases with higher expression of COX-2 and a higher COX-2/COX-1 ratio. The results suggest that at least part of the protective effect of NSAIDs on the risk of colorectal adenoma involves a COX-mediated pathway.

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.

Bayesian modeling of complex metabolic pathways

Many chronic diseases are the result of a complex sequence of biochemical reactions involving exposures to various environmental agents, metabolized by a number of different genes. Routine epidemiologic analyses of such associations have tended to rely on standard contingency table or logistic regression methods, typically focusing on one variable at a time or pairwise combinations. We consider two statistical alternatives to this approach, one based on Bayesian model averaging, one based on pharmacokinetic modeling of the biochemical pathways. These approaches are illustrated using data from a case-control study of colorectal polyps in relation to tobacco smoking and consumption of well done red meat, both viewed as sources of heterocyclic amines and polycyclic aromatic hydrocarbons. The new analyses are structured in a manner that attempts to take advantage of prior knowledge of the metabolism of these classes of compounds and the various genes that regulate these pathways.

Meat intake and the recurrence of colorectal adenomas

A large multicenter randomized controlled trial was re-assessed to check whether meat intake and a reduction in its consumption are associated with recurrence of adenomatous polyps of the large bowel, which are precursors of most colorectal malignancies. All subjects (n = 1905; 958 interventions and 947 controls) had one or more histologically confirmed colorectal adenomas removed during a colonoscopy within 6 months before randomization. The subjects were followed-up for approximately 4 years after randomization and a colonoscopy for detecting adenomas was conducted at the 1st and 4th year after randomization. Dietary variables were assessed at baseline (T0) and in conjunction with annual visits at the end of the 1st (T1), 2nd (T2), 3rd (T3) and 4th (T4) years. Odds ratios using logistic regression models for meat variables were estimated based on the average intake at T0, T1, T2, T3 and T4 (prior to the T4 colonoscopy) as well as change (T0-T4) in intake. In the intervention group, the total reduction in median intake of red meat from T0 to T4 was observed by the end of 1st year itself (30 and 31% for men and women, respectively). The analysis provide no evidence to suggest that lower intake or reduction in total and in red meat consumption during a period of 4 years reduces the risk of adenoma recurrence (including multiple or advanced adenoma), whereas the data suggest that high intake of fish is associated with lower risk of adenoma recurrence.

Effect of diet, life style, and other environmental/chemopreventive factors on colorectal cancer development, and assessment of the risks

This review presents a comprehensive, evenhanded evaluation of the evidence from experimental, in vitro and human studies associating environmental and therapeutic factors with risk of colorectal cancer. Life styles correlated with the greatest increase in colorectal cancer risk are the ones that typify a diet rich in fat and calories, alcohol drinking and tobacco smoking, and low intake of vegetable, fruits and fibers, referred to as a "western diet," as well as sedentary style (i.e., no- or low-exercise). This kind of life style has also been associated with other chronic diseases (other cancers, obesity, dyslipedemia, diabetes, hypertension cardiovascular, and hypertension). The evidence does not implicated red meat as a risk factor, and fiber has been shown to protect against colorectal adenomas and carcinomas. Calcium, vitamin D, folate, and some antioxidant vitamins and minerals (gamma-tocopherol and selenium) have protective effects, and daily exercise for > or =30 min results in a significant decrease in risk. Estrogen use (hormone replacement therapy) substantially reduces colorectal cancer risk in postmenopausal women. Nonsteroidal anti-inflammatory drugs (e.g., aspirin) in excessive doses is protective, especially in high risk populations, but the side effects of its use and cost incurred due to its continued intake over long periods must be carefully scrutinized before any recommendations are made for the general public.

Dietary fibre and colorectal adenoma in a colorectal cancer early detection programme

BACKGROUND

Although dietary fibre has been reported to have no association with colorectal adenoma and cancer, in some studies this topic remains controversial.

METHODS

We used a 137-item food frequency questionnaire to assess the relation of fibre intake and frequency of colorectal adenoma. The study was done within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a randomised controlled trial designed to investigate methods for early detection of cancer. In our analysis, we compared fibre intake of 33971 participants who were sigmoidoscopy-negative for polyps, with 3591 cases with at least one histologically verified adenoma in the distal large bowel (ie, descending colon, sigmoid colon, or rectum). Odds ratios were estimated by logistic regression analysis.

FINDINGS

High intakes of dietary fibre were associated with a lower risk of colorectal adenoma, after adjustment for potential dietary and non-dietary risk factors. Participants in the highest quintile of dietary fibre intake had a 27% (95% CI 14-38, p(trend)=0.002) lower risk of adenoma than those in the lowest quintile. The inverse association was strongest for fibre from grains and cereals and from fruits. Risks were similar for advanced and non-advanced adenoma. Risk of rectal adenoma was not significantly associated with fibre intake.

INTERPRETATION

Dietary fibre, particularly from grains, cereals, and fruits, was associated with decreased risk of distal colon adenoma.

Screening, prevention and socioeconomic costs associated with the treatment of colorectal cancer

Colorectal cancer (CRC), the third most prevalent cancer worldwide, imposes a significant economic and humanistic burden on patients and society. One study conservatively estimated the annual expenditures for colorectal cancer to be approximately dollars US 5.3 billion in 2000, including both direct and indirect costs. However, other investigators estimated inpatient costs alone incurred in the US in 1994 to be around dollars US 5.14 billion. Therefore, the economic burden of colorectal cancer in the US could be projected to be somewhere in the range of dollars US 5.5-6.5 billion by considering that inpatient costs approximate 80% of total direct costs. No worldwide data have been published, but assuming that the US represents 25-40% of total expenditures in oncology, as seen for breast and lung cancers, a rough estimate for colorectal cancer would be in the range of dollars US 14-22 billion. Screening helps increase patient survival by diagnosing colorectal cancer early. The ideal method among the four tests most used (faecal occult blood test, flexible sigmoidoscopy, colonoscopy and double contrast barium enema) has not been identified. Economic studies of colorectal cancer screening are complex because of the many variables involved, as well as the fact that the outcomes must be followed for many years, and the lack of consensus on screening guidelines. Intuitively, modelling colorectal cancer is one way to overcome these hurdles; published modelling studies predict colorectal cancer screening programs to be within the threshold of dollars US 40000 per life-year saved. The faecal occult blood test appears to be the only clearly effective test, both from a clinical and an economic viewpoint. Important limitations are the invasiveness and inconvenience of the screening procedures, except faecal occult blood test. Patients' comfort and satisfaction are essential in improving compliance with screening recommendations, which appears to be low even in the US (35% of the general population aged over 40 years and 60% of the high-risk population), the country with the highest awareness and compliance in the world. Since colorectal cancer is generally a disease of the elderly, its economic burden is expected to grow in the near future, mainly due to population aging. Potential avenues to pursue in order to contain or reduce the economic burden of colorectal cancer would be the design and implementation of efficient screening programmes, the improvement of patient awareness and compliance with screening guidelines, the development of appropriate prevention programs (i.e. primary and secondary), and earlier diagnosis.

Fat, fiber, fruits, vegetables, and risk of colorectal adenomas

A case-control study was conducted at the National Naval Medical Center (Maryland, USA) from 1994 to 1996 to investigate the possible association between dietary factors and colorectal adenomas. Cases (n = 239) were subjects diagnosed with adenomas (146 new and 93 recurrent) by sigmoidoscopy or colonoscopy. Those with no evidence of adenomas found by sigmoidoscopy were recruited as controls (n = 228). Dietary variables, assessed by a 100-item food frequency questionnaire, were analyzed by the logistic regression model, which was adjusted for age, gender and total energy intake. Variables of fat intake were further adjusted for red meat intake. An increased risk of 7% [odds ratio (OR): 1.07; 95% confidence interval (95% CI): 0.94-1.22] per 5% energy/day from total fat was observed. Every additional 5% unit of oleic acid intake/day significantly increased the adenoma risk by 115% (OR: 2.15; 95% CI: 1.05-4.39). Red meat fat increased the risk by 20% (OR: 1.20; 95% CI: 0.71-2.04), and white meat fat decreased the risk by 67% (OR: 0.33; 95% CI: 0.19-0.95) for every additional 5% unit of respective intake/day. Risk decreased by 41% (OR: 0.59; 95% CI: 0.41-0.86) for every additional 5% unit of fiber intake/day. Vegetable [OR per 100 g of vegetable intake/day: 0.83, 95% CI: 0.67-1.04] and fruit (OR per 100 g of fruit intake/day: 0.92, 95% CI: 0.82-1.03) intake showed an inverse association, and the results are suggestive of an association with the risk for adenomas. In conclusion, a strong positive association between oleic acid intake and colorectal adenoma risk was observed. This is likely to be an indicator of "unhealthy" food (meat, dairy, margarine, mayonnaise, sweet baked food) consumption in this population. Increased intake of dietary fiber was associated with a moderately decreased risk of adenomas.

Serum 25-hydroxyvitamin D, dietary calcium intake, and distal colorectal adenoma risk

Vitamin D has recently emerged as a potentially protective agent against colorectal neoplasia. We assessed the associations between dietary vitamin D, plasma 25-hydroxyvitamin D [25(OH)D], dietary calcium, and colorectal adenomas in a large screening sigmoidoscopy-based case-control study in Southern California. Because conversion of serum 25(OH)D to serum 1,25-vitamin D is highly regulated by serum calcium, we also assessed modification of the 25(OH)D-adenoma association by calcium intake. Cases were 473 subjects with a primary adenoma, and controls were 507 subjects who had no adenomas at sigmoidoscopy and no history of adenomas. Compared with those in the lowest quartile of intake, those in the highest quartile of dietary vitamin D had an adjusted odds ratio (OR) of 0.83 [95% confidence interval (CI) = 0.49-1.41] and those in the highest quartile of dietary calcium had an OR of 0.82 (95% CI = 0.49-1.25). There was a suggestion that plasma 25(OH)D may be protective in this population (OR for highest vs. lowest quartile = 0.74, 95% CI = 0.51-1.09). A significant protective effect of 25(OH)D was clearly evident only in those with calcium intakes below (OR = 0.40 for highest vs. lowest quartile, 95% CI = 0.22-0.71, p for trend = 0.005) and above (OR = 1.17, 95% CI = 0.69-1.99, p for trend = 0.94) the median calcium intake.