Cigarette smoking and adenomatous polyps: a meta-analysis

Annual report to the nation on the status of cancer, 1975-2006, featuring colorectal cancer trends and impact of interventions (risk factors, screening, and treatment) to reduce future rates

BACKGROUND

The American Cancer Society, the Centers for Disease Control and Prevention (CDC), the National Cancer Institute (NCI), and the North American Association of Central Cancer Registries (NAACCR) collaborate annually to provide updated information regarding cancer occurrence and trends in the United States. This year's report includes trends in colorectal cancer (CRC) incidence and death rates and highlights the use of microsimulation modeling as a tool for interpreting past trends and projecting future trends to assist in cancer control planning and policy decisions.

METHODS

Information regarding invasive cancers was obtained from the NCI, CDC, and NAACCR; and information on deaths was obtained from the CDC's National Center for Health Statistics. Annual percentage changes in the age-standardized incidence and death rates (based on the year 2000 US population standard) for all cancers combined and for the top 15 cancers were estimated by joinpoint analysis of long-term trends (1975-2006) and for short-term fixed-interval trends (1997-2006). All statistical tests were 2-sided.

RESULTS

Both incidence and death rates from all cancers combined significantly declined (P < .05) in the most recent time period for men and women overall and for most racial and ethnic populations. These decreases were driven largely by declines in both incidence and death rates for the 3 most common cancers in men (ie, lung and prostate cancers and CRC) and for 2 of the 3 leading cancers in women (ie, breast cancer and CRC). The long-term trends for lung cancer mortality in women had smaller and smaller increases until 2003, when there was a change to a nonsignificant decline. Microsimulation modeling demonstrates that declines in CRC death rates are consistent with a relatively large contribution from screening and with a smaller but demonstrable impact of risk factor reductions and improved treatments. These declines are projected to continue if risk factor modification, screening, and treatment remain at current rates, but they could be accelerated further with favorable trends in risk factors and higher utilization of screening and optimal treatment.

CONCLUSIONS

Although the decrease in overall cancer incidence and death rates is encouraging, rising incidence and mortality for some cancers are of concern.

Visceral fat area and markers of insulin resistance in relation to colorectal neoplasia

OBJECTIVE

Although abdominal obesity and related metabolic abnormalities are hypothesized to promote colorectal carcinogenesis, direct confirmation of this effect is required. Here, we examined the relation of early-stage colorectal neoplasia to visceral fat area and markers of insulin resistance.

RESEARCH DESIGN AND METHODS

Subjects were participants in a comprehensive health screening conducted at the Hitachi Health Care Center, Ibaraki, Japan. During a 3-year period (2004-2007), a total of 108 patients with early-stage colorectal neoplasia, including 22 with early cancer, were identified among individuals who received both colorectal cancer screening and abdominal computed tomography scanning. Three control subjects matched to each case subject were randomly selected from those whose screening results were negative. Conditional logistic regression analysis was used to examine the association of measures of obesity and markers of insulin resistance with colorectal neoplasia, with adjustment for smoking and alcohol drinking.

RESULTS

Visceral fat area, but not subcutaneous fat area, was significantly positively associated with colorectal cancer, with odds ratios (95% CI) for the lowest to highest tertile of visceral fat area of 1 (reference), 2.17 (0.45-10.46), and 5.92 (1.22-28.65), respectively (P(trend) = 0.02). Markers of insulin resistance, particularly fasting glucose, were also positively associated with colorectal cancer risk. In contrast, no associations were observed for colorectal adenomas.

CONCLUSIONS

These results suggest that visceral adipose tissue accumulation and insulin resistance may promote the development of early-stage cancer but not adenoma in the colorectum.

DNA/RNA markers for colorectal cancer risk in preserved stool specimens: a pilot study

AIMS AND BACKGROUND

Exfoliated cells in human stool offer excellent opportunities to non-invasively detect molecular markers associated with colorectal tumorigenesis, and to evaluate the effects of exposures to exogenous and endogenous carcinogenic or chemopreventive substances. This pilot study investigated the feasibility of determining DNA methylation and RNA expression simultaneously in stool specimens treated with a single type of nucleic acid preservatives.

METHODS

Stool specimens from 56 volunteers that were preserved up to a week with RNA later were used in this study. Bisulfite sequencing was used to determine methylation at 27 CpG loci on the estrogen receptor 1 (ESR1) promoter. Taqman assay was used for quantitative reverse transcription polymerase chain reactions to measure cyclooxygenase 2 (COX2) and epidermal growth factor receptor (EGFR) mRNA expression. Subjects' basic demographic and other selected risk factors for colorectal cancer were captured through questionnaires and correlated with the levels of these markers.

RESULTS

Less than 10% of the samples failed in individual assays. Overall, 24.0% of the CpG loci on the ESR1 promoter were methylated. COX2 expression and alcohol use were positively correlated; an inverse association was present between EGFR expression and cigarette smoking; and subjects using anti-diabetic medication had higher ESR1 methylation. In addition, higher EGFR expression levels were marginally associated with history of polyps and family history of colorectal cancer.

CONCLUSIONS

The present study demonstrates that simultaneous analyses for DNA and RNA markers are feasible in stool samples treated with a single type of nucleotide preservatives. Among several associations observed, the association between EGFR expression and polyps deserves further investigation as a potential target for colorectal cancer screening. Larger studies are warranted to confirm some of our observations.

Smokers as a high-risk group: data from a screening population

GOAL

To determine the number of pack-years exposure associated with a 2-fold increase risk for significant colorectal neoplasia and to examine the risk of smoking in younger patients.

BACKGROUND

Cigarette smoking has been shown to be a significant risk factor for colorectal neoplasia and may be used to stratify patients for screening or triaging of screening resources. However, more information is needed regarding the amount of exposure required to significantly increase by 2-fold an individual's risk for colorectal neoplasia.

METHODS

Data collected for 2707 patients presenting for screening colonoscopy included tobacco use measured in pack-years and known risk factors for colorectal neoplasia. Our outcome was endoscopically detected significant colorectal neoplasia that included large (>1 cm) tubular adenomas, villous adenomas, multiple (3 or more) adenomas, high-grade dysplasia, and adenocarcinoma.

RESULTS

Patients who smoked more than 30 pack-years were more than 2 times more likely to have significant colorectal neoplasia than patients who never smoked (odds ratio: 2.40; 95% confidence interval: 1.65-3.50). For patients aged 40 to 49 years, smokers were more likely than nonsmokers to have significant colorectal neoplasia (odds ratio: 2.71; 95% confidence interval: 1.05-6.97).

CONCLUSIONS

Patients who have smoked more than 30 pack-years had a more than 2-fold increase for significant colorectal neoplasia as compared with nonsmokers. The increased risk was also observed in younger patients. Our data have implications for screening guidelines.

Cigarette smoking and K-ras mutations in pancreas, lung and colorectal adenocarcinomas: etiopathogenic similarities, differences and paradoxes

Surprisingly different frequencies and patterns of K-ras mutations are observed in human adenocarcinomas of the pancreas, colorectum and lung. Their respective relationships with smoking are apparently paradoxical. We evaluated all the available types of clinical and epidemiological studies on the relationship between tobacco smoking and the occurrence of K-ras mutations in human adenocarcinomas of the pancreas, colorectum and lung. We identified 8, 7 and 12 studies that analyzed the relationship between K-ras mutations and tobacco smoking in human neoplasms of the pancreas, colorectum and lung, respectively. A meta-analysis was undertaken for each site separately. In pancreatic adenocarcinomas lifetime history of tobacco consumption was not significantly associated with the frequency of K-ras mutations (OR=1.26; 95% CI=0.82-1.94). Similarly, no association was observed between smoking and K-ras mutations in colorectal adenocarcinomas (OR=0.94; CI=0.79-1.12), neither when colorectal adenomas and adenocarcinomas were jointly analyzed (OR=0.96; 95% CI=0.83-1.13). In lung adenocarcinoma, where only 15-25% of cases harbor a K-ras mutation, tumors from smokers were more likely to have K-ras mutations than tumors from non-smokers (OR=3.67; 95% CI=2.47-5.45). Furthermore, in lung adenocarcinomas K-ras mutations have a pattern different from that in pancreatic and colorectal adenocarcinomas. Results support the hypothesis that smoking influences the risk of pancreatic cancer - and possibly colorectal cancer - through events other than K-ras mutations. In adenocarcinoma of the lung, smoking may play a role in the occurrence of K-ras mutations. If the influence of tobacco products in the induction, acquisition and persistence of K-ras mutations had some tissue specificity, or was dependent on different factors in different organs, the corresponding mechanisms would deserve detailed research.

Meat and heterocyclic amine intake, smoking, NAT1 and NAT2 polymorphisms, and colorectal cancer risk in the multiethnic cohort study

BACKGROUND

N-acetyltransferases (NAT) 1 and 2 are polymorphic enzymes catalyzing the metabolic activation of heterocyclic amines. We investigated the modifying effects of NAT1 and NAT2 polymorphisms on the association of meat consumption, heterocyclic amine intake, and smoking with colorectal cancer risk.

METHOD

In the Multiethnic Cohort study, participants completed a smoking history and a food-frequency questionnaire at recruitment and a cooked meat module 5 years later to estimate heterocyclic amine intake (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline). Blood samples were collected from incident cases and age-, sex-, ethnicity-, frequency-matched controls to determine genotypes. For analysis of meat intake and smoking, data were available for 1,009 cases and 1,522 controls; for heterocyclic amine intake analyses, 398 cases and 1,444 controls were available. Multivariate logistic regression models were used to estimate odds ratios.

RESULTS

Smoking was associated with an increased colorectal cancer risk (odds ratio, 1.51; 95% confidence interval, 1.17-1.95) for > or =30 pack-years compared with never smokers (P trend = 0.0004). The association was stronger with presence of the "rapid" compared with the "slow/intermediate" NAT2 genotype (P interaction = 0.003). No significant associations were observed for intakes of red meat, processed meat, and heterocyclic amine, or meat doneness preference, but a dietary pattern high in meat showed a weak positive interaction with the NAT2 genotype (P interaction = 0.05).

CONCLUSION

The enhanced association between smoking and colorectal cancer risk in subjects with the NAT2 rapid genotype supports a role for NAT2 and tobacco smoke heterocyclic amines in the etiology of colorectal cancer. This study only provides weak support for a similar association with meat heterocyclic amines.

Cigarette smoking and the risk of colorectal cancer: a meta-analysis of prospective cohort studies

BACKGROUND & AIMS

Smoking has been implicated in many malignant diseases, but its association with colorectal cancer (CRC) is controversial. We quantitatively evaluated the relation between smoking and incidence of CRC in a meta-analysis of cohort studies.

METHODS

Full publications of prospective cohort studies were identified in MEDLINE and EMBASE from 1950 to 2008. Subjects were classified as current smokers, former smokers, or never smokers. The quantity of smoking was assessed by number of cigarettes per day, years of smoking, and pack-years. The reported relative risks of CRC were pooled by random-effects model. Sensitivity analysis was conducted, and publication bias was evaluated.

RESULTS

A total of 1,463,796 subjects were recruited in 28 prospective cohorts from America, Europe, and Asia, with median follow-up of 13 years (range, 4-30 years). Current smokers showed a modestly higher risk of CRC (relative risk [RR], 1.20; 95% confidence interval [CI], 1.10-1.30) than never smokers. The risk of CRC among male smokers (RR, 1.38; 95% CI, 1.22-1.56) was more significant than among female smokers (RR, 1.06; 95% CI, 0.95-1.19). Rectal cancer was more closely related to smoking (RR, 1.36; 95% CI, 1.15-1.61) than colonic cancer. Former smokers still carried a higher CRC risk than never smokers. The increased risk of CRC was related to cigarettes per day, longer years of smoking, or larger pack-years.

CONCLUSIONS

Smoking was associated with a significantly increased risk of CRC. The associated risk was higher for men and for rectal cancers. The association of tobacco consumption and CRC risk appeared to be dose-related.

Gender as a risk factor for advanced neoplasia and colorectal cancer: a systematic review and meta-analysis

BACKGROUND & AIMS

Studies have reported higher rates of advanced colorectal neoplasia in men than in women. We performed a meta-analysis to provide a quantitative pooled risk estimate of the association between gender and advanced colorectal neoplasia.

METHODS

We conducted a systematic review to identify studies of average risk and asymptomatic individuals undergoing screening colonoscopy. We also included studies of subjects with a family history of colorectal neoplasia. We used random effects models to evaluate pooled relative risk estimates and performed heterogeneity and publication bias analyses. The primary outcome measure was relative risk of advanced neoplasia in men compared with women. A secondary outcome measure was relative risk for colorectal cancer.

RESULTS

Seventeen studies consisting of 18 different populations were included, comprising 924,932 men and women. The pooled relative risk estimate for advanced neoplasia for men compared with women was 1.83 (95% confidence interval [CI], 1.69 -1.97). This positive association between gender and advanced neoplasia was significant across all age groups from 40 to older than 70 years. In 5 studies, the relative risk estimate for cancer for men compared with women was 2.02 (95% CI, 1.53-2.66). Significant heterogeneity was found for the overall analysis and for studies reporting on cancer but not for studies thate xcluded subjects with a family history or for those analyses grouped by age.

CONCLUSIONS

This meta-analysis provides strong evidence that men are at greater risk for advanced colorectal neoplasia across all age groups. This might inform decisions to create sex-specific colorectal cancer screening recommendations.

Cigarette smoking and colorectal cancer incidence and mortality: systematic review and meta-analysis

The association between cigarette smoking and colorectal cancer (CRC) has been controversial. To synthesize the available data, we conducted a comprehensive meta-analysis of all prospective studies. A total of 36 studies were included in our meta-analysis. We examined the association between smoking and CRC, colon cancer and rectal cancer in terms of incidence and mortality. Separate analyses were conducted for smoking status, daily cigarette consumption, duration, pack-years and age of initiation. Relative to nonsmokers, current and former smokers had a significantly increased risk of CRC incidence and mortality, respectively. When CRC data were combined with colon/rectal cancer data, current smokers had a significantly increased risk of CRC incidence. All 4 dose-response variables examined-daily cigarette consumption (RR = 1.38 for an increase of 40 cigarettes/day), duration (RR = 1.20 for an increase of 40 years of duration), pack-years (RR = 1.51 for an increase of 60 pack-years) and age of initiation (RR = 0.96 for a delay of 10 years in smoking initiation)-were significantly associated with CRC incidence (all p-values < 0.0001). The relationship between duration of smoking and rectal cancer incidence was also significant. Among the subset of studies that distinguished cancer by site, a higher risk was seen for rectal cancer than for colon cancer for all analyses. Among prospective studies, a consistent association exists between smoking and CRC. The association is stronger for rectal cancer than for colon cancer in the subset of studies that differentiated cancer by site.

The epidemiology and pathogenesis of neoplasia in the small intestine

PURPOSE

The mucosa of the small intestine encompasses about 90% of the luminal surface area of the digestive system, but only 2% of the total annual gastrointestinal cancer incidence in the United States.

METHODS

The remarkable contrast in age-standardized cancer incidence between the small and large intestine has been reviewed with respect to the cell type patterns, demographic features, and molecular characteristics of neoplasms.

RESULTS

Particularly noteworthy is the predominance of adenocarcinoma in the colon, which exceeds 98% of the total incidence by cell type, in contrast to that of 30% to 40% in the small intestine, resulting in an age-standardized ratio of rates exceeding 50-fold. The prevalence of adenomas and carcinomas is most prominent in the duodenum and proximal jejunum. The positive correlation in global incidence rates of small and large intestinal neoplasms and the reciprocal increases in risk of second primary adenocarcinomas suggest that there are common environmental risk factors. The pathophysiology of Crohn inflammatory bowel disease and the elevated risk of adenocarcinoma demonstrate the significance of the impaired integrity of the mucosal barrier and of aberrant immune responses to luminal indigenous and potentially pathogenic microorganisms.

CONCLUSION

In advancing a putative mechanism for the contrasting mucosal susceptibilities of the small and large intestine, substantial differences are underscored in the diverse taxonomy, concentration and metabolic activity of anaerobic organisms, rate of intestinal transit, changing pH, and the enterohepatic recycling and metabolism of bile acids. Experimental and epidemiologic studies are cited that suggest that the changing microecology, particularly in the colon, is associated with enhanced metabolic activation of ingested and endogenously formed procarcinogenic substrates.

Serum nutrients and habitual dietary intake in colectomized FAP patients in Norway

BACKGROUND

Patients with familial adenomatous polyposis (FAP) are colectomized in young age in order to avoid development of colorectal cancer. Because colectomy radically changes gastrointestinal physiology, and food avoidance may be present, colectomized patients may be at risk for nutritional deficiency.

AIM OF THE STUDY

to evaluate: (1) serum biochemical levels as compared to reference; (2) dietary intake as compared to the recommendations.

METHODS

Blood samples, interviews and food frequency questionnaire were collected from 38 colectomized FAP patients with duodenal adenomas (mean age 40 years, range: 24-70). They were recruited from the Norwegian database on FAP.

RESULTS

Serum albumin was significantly higher (P < or = 0.0001), and Mg (P = 0.02), ferritin (P < or = 0.001), and cholesterol (P = 0.03) significantly lower, than reference levels. Compared to recommendations, a low intake was seen for folate and fiber (<50%), iron, thiamin, riboflavin (< 25%), and omega-3 fatty acids (8%). Sugar intake exceeded the recommendation, mainly due to a high intake of soft drinks. Food avoidance was reported by 53%.

CONCLUSIONS

We would suggest that the nutrient intake among FAP patients should at least meet the recommendations for healthy subjects. Their risk of metachronous cancers should also cause special attention to dietary factors that may prevent nutritional deficiency and carcinogenesis.

Association of tobacco and alcohol use with earlier development of colorectal cancer: should we modify screening guidelines?

BACKGROUND

Current guidelines recommend initial colorectal cancer screening at age 50 years for average-risk patients. Alcohol and tobacco use can be associated with earlier onset of colorectal cancer. We hypothesized an earlier age at diagnosis and/or more advanced stage in patients with these habits.

METHODS

We queried our tumor registry for colorectal cancer diagnosed between January 1997 and December 2006. Data were analyzed to evaluate effects of alcohol and tobacco use.

RESULTS

Of 335 colorectal cancer patients, 81% used tobacco, 51% used alcohol, 45% used both, and 14% used neither. Current tobacco and alcohol use were associated with younger ages at onset of colorectal cancer. Thirteen of 332 patients were diagnosed with colorectal cancer before age 50 years. All had exposure to alcohol and tobacco. Fifty-four percent (7/13) of these patients presented at stage 3/4 compared with 34% of the overall population.

CONCLUSIONS

Modification of screening guidelines to include these habits as "high-risk" factors may be indicated.

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.

Colorectal polyps: the scope and management of the problem

Colorectal cancer affects over 150,000 individuals yearly, and accounts for over 50,000 deaths. Much of the benefit of colorectal cancer screening has been attributed to detection and removal of adenomatous polyps, highlighting the importance of colorectal polyps as targets for intervention and as biomarkers for colorectal cancer risk. This review details the epidemiology of sporadic colorectal polyps, rationale behind use of polyps as an important surrogate for colorectal cancer risk, the benefits and limitations of secondary prevention of colorectal polyps through chemopreventive and dietary interventions, as well as colon surveillance.

Factors that increase risk of colon polyps

Adenomatous polyps are common and factors that increase risk include race, gender, smoking, and obesity. This author summarizes the evidence supporting increased risk with these factors and describes how epidemiological data may be used to tailor screening programs.

Pooled analysis of genetic variation at chromosome 8q24 and colorectal neoplasia risk

Several different genetic variants at chromosome 8q24 have been related to prostate, breast and colorectal cancer risk with evidence of region-specific risk differentials for various tumor types. We investigated the association between 15 polymorphisms located in 8q24 regions associated with cancer risk in a pooled analysis of 2587 colorectal adenoma cases, 547 colorectal cancer cases and 2798 controls of European descent from four studies. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for the associations. Three polymorphisms (rs10808555, rs6983267 and rs7837328) located between 128.47 and 128.54 Mb were found to be associated with colorectal tumor risk. The association was strongest for the previously reported rs6983267 variant and was similar for both adenoma (OR(per allele) = 1.16, 95% CI: 1.07-1.25, P = 0.0002) and cancer (OR (per allele) = 1.17, 95% CI: 1.01-1.35, P = 0.03). The strength of the association of the regional haplotype containing variant alleles at rs10808555, rs6983267 and rs7837328 but not rs10505476 was greater than that of any single variant of both adenoma (OR = 1.27, P = 0.0001) and cancer (OR = 1.26, P = 0.03). The risk associated with rs6983267 was stronger for multiple adenomas (OR(per allele) = 1.29, P = 5.6 x 10(-6)) than for single adenoma (OR(per allele) = 1.10, P = 0.03) with P(heterogeneity) = 0.008. This study confirms the association between colorectal neoplasia and the 8q24 polymorphisms located between 128.47 and 128.54 Mb and suggests a role for these variants in the formation of multiple adenomas.