Cigarette smoking and the risk of colorectal cancer in women

Effects of interactions between common genetic variants and smoking on colorectal cancer

Background

Although genome-wide association studies (GWAS) have identified variants in approximately 40 susceptibility loci for colorectal cancer (CRC), there are few studies on the interactions between identified single-nucleotide polymorphisms (SNPs) and lifestyle risk factors. We evaluated whether smoking could modify associations between these genetic variants and CRC risk.

Methods

A total of 703 CRC patients and 1406 healthy controls were included in this case-control study from the National Cancer Center in Korea. Thirty CRC susceptibility SNPs identified in previous GWAS were genotyped. A logistic regression model was used to examine associations between the SNPs and smoking behaviors by sex. The interaction was estimated by including an additional interaction term in the model.

Results

In men, an increased CRC risk was observed for longer durations (OR_{>28 vs. ≤28years} = 1.49 (95% CI = 1.11–1.98)), greater quantities (OR_{≥20 vs. <20cigarettes/day} = 2.12 (1.61–2.79)), and longer pack-years of smoking (OR_{≥21 vs. <21pack-years} = 1.78 (1.35–2.35)). In women, longer pack-years of smoking significantly increased CRC risk (OR_{≥5 vs. <5pack-years} = 6.11 (1.10–34.00)). Moreover, there were significant interactions between smoking status and the polymorphisms rs1957636 at 14q22.3 (P_interaction = 5.5 × 10⁻⁴) and rs4813802 at 20p12.3 (P_interaction = 0.04) in men. Interactions between smoking status and the rs6687758 at 1q41 (P_interaction = 0.03), duration and the rs174537 at 11q12.2 (P_interaction = 0.05), and pack-years and the rs4813802 (P_interaction = 0.04) were also found in women.

Conclusions

Associations between susceptibility SNPs and CRC risk may be modified by smoking behaviors, supporting the existence of gene-smoking interactions.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3886-0) contains supplementary material, which is available to authorized users.

Cigarette smoking and the risk of nasopharyngeal carcinoma: a meta-analysis of epidemiological studies

OBJECTIVE

The role of cigarette smoking as an independent risk factor for patients with nasopharyngeal carcinoma (NPC) is controversial. We attempted to provide evidence of a reliable association between cigarette smoking and the risk of NPC.

DESIGN

Meta-analysis.

DATA SOURCES

PubMed online and the Cochrane Library of relevant studies published up to February 2016.

ELIGIBILITY CRITERIA

All studies had to evaluate the relationship between NPC and cigarette smoking with never smokers as the reference group.

OUTCOMES

The primary outcome was the adjusted OR, RR or HR of NPC patients comparing smoking with never-smoking; the second was the crude OR, RR or HR.

RESULTS

We identified 17 case-control studies and 4 cohort studies including 5960 NPC cases and 429 464 subjects. Compared with never smokers, current smokers and ever smokers had a 59% and a 56% greater risk of NPC, respectively. A dose-response relationship was identified in that the risk estimate rose by 15% (p<0.001) with every additional 10 pack-years of smoking, and risk increased with intensity of cigarette smoking (>30 cigarettes per day). Significantly increased risk was only found among male smokers (OR, 1.36; 95% CI 1.15 to 1.60), not among female smokers (OR, 1.58; 95% CI 0.99 to 2.53). Significantly increased risk also existed in the differentiated (OR, 2.34; 95% CI 1.77 to 3.09) and the undifferentiated type of NPC (OR, 1.15; 95% CI 0.90 to 1.46). Moreover, people who started smoking at younger age (<18 years) had a greater risk than those starting later for developing NPC (OR, 1.78; 95% CI 1.41 to 2.25).

CONCLUSIONS

Cigarette smoking was associated with increased risk of NPC, especially for young smokers. However, we did not find statistical significant risks of NPC in women and in undifferentiated type, which might warrant further researches.

Epidemiological evidence on environmental tobacco smoke and cancers other than lung or breast

We reviewed 87 epidemiological studies relating environmental tobacco smoke (ETS) exposure to risk of cancer other than lung or breast in never smoking adults. This updates a 2002 review which also considered breast cancer. Meta-analysis showed no significant relationship with ETS for nasopharynx cancer, head and neck cancer, various digestive cancers (stomach, rectum, colorectal, liver, pancreas), or cancers of endometrium, ovary, bladder and brain. For some cancers (including oesophagus, colon, gall bladder and lymphoma) more limited data did not suggest a relationship. An increased cervix cancer risk (RR 1.58, 95%CI 1.29-1.93, n = 17 independent estimates), reducing to 1.29 (95%CI 1.01-1.65) after restriction to five estimates adjusting for HPV infection or sexual activity suggests a causal relationship, as do associations with nasosinus cancer observed in 2002 (no new studies since), and less so kidney cancer (RR 1.33, 95%CI 1.04-1.70, n = 6). A weaker association with total cancer (RR 1.13, 95%CI 1.03-1.35, n = 19) based on heterogeneous data is inconclusive. Inadequate confounder control, recall bias, publication bias, and occasional reports of implausibly large RRs in individual studies contribute to our conclusion that the epidemiological evidence does not convincingly demonstrate that ETS exposure causes any of the cancers studied.

Passive Smoking and Risk of Colorectal Cancer

We conducted this meta-analysis to explore the association between passive smoking and the risk of colorectal cancer. A literature search of online databases, including MEDLINE, EMBASE, the Cochrane Library, and Web of Science was performed up to June 30, 2015. A fixed-effects meta-analysis using Stata 12.0 was carried out to estimate the relative risks (RRs) and 95% confidence intervals (CIs) for the associations. Eleven articles, including 6 case-control studies and 6 cohort studies, were included in our analysis according to inclusion and exclusion criteria. The pooled RR of all studies showed a statistically significant association between passive smoking and colorectal cancer (RR = 1.14; 95% CI = 1.05-1.24). Results of subgroup analysis showed a positive association between passive smoking and rectal cancer ((RR = 1.33; 95% CI = 1.15-1.53) and that male passive smokers were at greater risks of colorectal cancer (RR = 1.73; 95% CI = 1.37-2.19) than females. Results suggested that passive smoking is associated with an increased risk of colorectal cancer.

Metabolites of tobacco smoking and colorectal cancer risk

Colorectal cancer is not strictly considered a tobacco-related malignancy, but modest associations have emerged from large meta-analyses. Most studies, however, use self-reported data, which are subject to misclassification. Biomarkers of tobacco exposure may reduce misclassification and provide insight into metabolic variability that potentially influences carcinogenesis. Our aim was to identify metabolites that represent smoking habits and individual variation in tobacco metabolism, and investigate their association with colorectal cancer. In a nested case-control study of 255 colorectal cancers and 254 matched controls identified in the Prostate, Lung, Colorectal and Ovarian cancer screening trial, baseline serum was used to identify metabolites by ultra-high-performance liquid-phase chromatography and mass spectrometry, as well as gas chromatography with tandem mass spectrometry. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by logistic regression. Self-reported current smoking was associated with serum cotinine, O-cresol sulfate and hydroxycotinine. Self-reported current smoking of any tobacco (OR = 1.90, 95% CI: 1.02-3.54) and current cigarette smoking (OR = 1.51, 95% CI: 0.75-3.04) were associated with elevated colorectal cancer risks, although the latter was not statistically significant. Individuals with detectable levels of hydroxycotinine had an increased colorectal cancer risk compared with those with undetectable levels (OR = 2.68, 95% CI: 1.33-5.40). Although those with detectable levels of cotinine had a suggestive elevated risk of this malignancy (OR = 1.81, 95% CI: 0.98-3.33), those with detectable levels of O-cresol sulfate did not (OR = 1.16, 95% CI: 0.57-2.37). Biomarkers capturing smoking behavior and metabolic variation exhibit stronger associations with colorectal cancer than self-report, providing additional evidence for a role for tobacco in this malignancy.

Risk of colorectal cancer associated with active smoking among female teachers

PURPOSE

The objective of this study was to examine the risk of colorectal cancer associated with active smoking among members of the California Teachers Study (CTS), a large cohort of female public school employees for whom highly detailed smoking information is available.

METHODS

The analysis was conducted among the 122,264 CTS participants who lived in California at cohort entry in 1995/1996, had no prior history of colorectal cancer, and provided detailed smoking information. 1,205 cases of invasive colorectal cancer prospectively diagnosed in 1995-2009 were identified from the California Cancer Registry, including 650 in the proximal colon, 267 in the distal colon, and 288 in the rectum. Hazard ratios and 95% confidence intervals were estimated using Cox proportional hazards models, stratified by age at cohort entry, and adjusted for race/ethnicity.

RESULTS

Compared to never smokers, current smokers had an approximately 30% increased risk of colorectal cancer. Overall, a slightly elevated risk was also noted for former smokers. Among former smokers, risks appeared to remain elevated for up to 20 years following cessation. Risks among former and current smokers increased with greater intensity and duration of smoking. Little evidence for heterogeneity in risk was noted for colon versus rectal cancer or for different subsites within the colon.

CONCLUSIONS

These results provide convincing evidence that heavy and/or long-term smoking is a risk factor for cancers of the colon and rectum. Such evidence should be considered when updating screening guidelines to include targeting people with long active smoking histories.

The effect of secondhand smoke exposure on the association between active cigarette smoking and colorectal cancer

BACKGROUND

Studies published prior to 1980 failed to find an association between smoking and colorectal cancer, while subsequent studies reported an association after accounting for a three to four decade initiation period. The aims of this study were to determine the effect of accounting for secondhand smoke (SHS) exposure on the association between smoking and colorectal cancer and to determine the association between SHS and colorectal cancer.

METHODS

Approximately 1,200 colorectal cancer cases treated at Roswell Park Cancer Institute between 1982 and 1998 were matched to 2,400 malignancy-free controls. The effect of accounting for SHS exposure was determined by comparing the odds ratios (OR) for each smoking variable in the overall sample and then for those who reported no current SHS exposure.

RESULTS

A small, significant increase in colorectal cancer odds was noted for heavy, long-term smoking males when not accounting for SHS exposure (>45 PY: OR = 1.34; 95% CI 1.04-1.72). OR increased when the analyses were restricted to individuals reporting no current SHS exposure (>45 PY: OR = 2.40; 95% CI 1.36-4.23).

CONCLUSIONS

Accounting for SHS exposure resulted in a substantial increase in the odds of colorectal cancer for all smoking variables in this study. Future studies should account for SHS exposure when examining the association between smoking and colorectal cancer.

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.

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.

Morbidity and mortality in relation to smoking among women and men of Chinese ethnicity: the Singapore Chinese Health Study

OBJECTIVES

We examined the association among cigarette smoking, smoking cessation and a broad range of cancer incidence and all cause and cause-specific mortality in a population-based cohort of adults of Chinese ethnicity in Singapore.

METHODS

Subjects were 61,320 participants of the Singapore Chinese Health Study (44.5% men, aged 45-74 years, recruitment from 1993-1998) who were free of cancer at the baseline examination. Main outcomes-of-interest included cancer incidence, all cause and cause-specific mortality as of December 31, 2005.

RESULTS

Cigarette smoking was positively associated with overall cancer incidence, including cancers at the following specific sites: head and neck region, upper gastrointestinal tract, hepatobiliary and pancreas cancer, lung, and bladder/renal pelvis cancer. Compared to never smokers, the relative risk (RR) (95% confidence interval [CI]) of cancer incidence (all cancer sites) among current smokers smoking >22 cigarettes/day was 1.9 (1.7-2.1), p-trend<0.0001. Similarly, cigarette smoking was associated with all cause and cause-specific mortality, including deaths due to cancer, ischemic heart disease, other heart diseases, and chronic obstructive pulmonary disease. Compared to never smokers, RR (95%CI) of all cause mortality among current smokers smoking >22 cigarettes/day was 1.8 (1.6-2.0), p-trend<0.0001. Also, relative to current smokers, ex-smokers experienced reduced cancer incidence and total mortality. The population attributable risk of smoking in men for cancer incidence as well as all-cause mortality was 23%, whereas in women it ranged from 4-5%.

CONCLUSIONS

Cigarette smoking is an important risk factor for cancer incidence and major causes of mortality in Chinese men and women of Singapore.

Association between cigarette smoking and colorectal cancer in the Women's Health Initiative

The evidence linking cigarette smoking to the risk of colorectal cancer is inconsistent. We investigated the associations between active and passive smoking and colorectal cancer among 146,877 Women's Health Initiative participants. Women reported detailed smoking histories at enrollment. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for the association between smoking and overall and site-specific risk of colorectal cancer. Invasive colorectal cancer was diagnosed in 1242 women over an average of 7.8 years (range = 0.003-11.2 years) of follow-up. In adjusted analyses, statistically significant positive associations were observed between most measures of cigarette smoking and risk of invasive colorectal cancer. Site-specific analyses indicated that current smokers had a statistically significantly increased risk of rectal cancer (HR = 1.95, 95% CI = 1.10 to 3.47) but not colon cancer (HR = 1.03, 95% CI = 0.77 to 1.38), compared with never smokers. Passive smoke exposure was not associated with colorectal cancer in adjusted analyses. Thus, active exposure to cigarette smoking appears to be a risk factor for rectal cancer.

Effect of NAT1 and NAT2 genetic polymorphisms on colorectal cancer risk associated with exposure to tobacco smoke and meat consumption

N-Acetyltransferases 1 and 2 (NAT1 and NAT2), both being highly polymorphic, are involved in the metabolism of aromatic and heterocyclic aromatic amines present in cigarette smoke and red meat cooked by high-temperature cooking techniques. We investigated the effect of differences in acetylation capacity, determined by NAT1 and NAT2 genotypes, on colorectal cancer risk associated with exposure to tobacco smoke or red meat consumption. In this population-based case-control study in Germany, 505 patients with incident colorectal cancer and 604 age- and sex-matched control individuals with genotyping data and detailed risk factor information were included. Genotyping of NAT1 and NAT2 genetic polymorphisms was done using a fluorescence-based melting curve analysis method. The association between genotypes, environmental exposures, and colorectal cancer risk was estimated using multivariate logistic regression. Colorectal cancer risk associated with active smoking was elevated after accumulation of 30(+) pack-years of smoking [odds ratio (OR), 1.4; 95% confidence interval (95% CI), 0.9-2.2] but not significantly modified by either NAT1 or NAT2 genotype. Exposure to environmental tobacco smoke was associated with an increased risk for colorectal cancer only among NAT2 fast acetylators (OR, 2.6; 95% CI, 1.1-5.9 for exposure in childhood and adulthood). Frequent consumption of red meat significantly increased colorectal cancer risk for the group comprising all NAT2 fast acetylators or carriers of the NAT1*10 allele (OR, 2.6; 95% CI, 1.1-6.1) but not among those with "slow" NAT1 and NAT2 genotypes. Our findings indicate that NAT1 and NAT2 genotypes may contribute jointly to individual susceptibility and that heterocyclic aromatic amines may play an important role in colorectal cancer associated with red meat and possibly also exposure to environmental tobacco smoke.

Is it exposure to cigarette smoke or to smokers which increases the risk of meningococcal disease in teenagers?

BACKGROUND

Passive smoking appears to increase the risk of meningococcal disease (MD) in adolescents. Whether this effect is attributable to exposure to cigarette smoke or contact with smokers is unknown.

METHODS

We conducted a prospective population-based case-control study with age, sex matched-controls in 1:1 matching. Participants were 15-19 year old with MD recruited at hospital admission in six regions (65% of the population of England) from January 1999 through June 2000, and their matched controls. Data on potential risk factors were gathered by confidential interview, including seven passive smoking variables. Factor analysis was performed to assess the dimensionality of the passive smoking exposure variables. The data were analysed with univariate and multivariate conditional logistic regression.

RESULTS

144 case-control pairs were recruited (51% male; median age 17.6). Factor analysis identified two independent factors representing passive smoking (P < 0.01), one associated with 'exposure to smoke', the other with 'smoker contact'. Only smoker contact was a significant risk factor for MD (OR = 1.8; 95% CI 1.0-3.3; P = 0.05). In multivariate analysis this factor was still associated with MD independently of potential confounders such as active smoker status and household crowding.

CONCLUSION

Contact with smokers is associated with increased risk of MD in adolescents. This is more likely to be due to higher carriage rates in smokers than to exposure to smoke and emphasizes the importance of public health measures to stop smoking. In epidemiological studies that assess risk from passive smoking, exposure to smoke should be differentiated where possible from contact with smokers.

Environmental tobacco smoke and cancer of sites other than the lung in adult non-smokers

Evidence from epidemiological studies relating environmental tobacco smoke (ETS) exposure to risk of cancer of sites other than the lung in adult non-smokers is reviewed. Problems common to many studies include small sample size, inadequate control of potential confounding, failure to consider the possibility of misclassification of smoking status, reliance on death certificate diagnosis, use of proxy respondents and the possibility of recall bias. A number of the studies have other obvious weaknesses. Publication bias is known to be a problem, with two very large prospective studies having reported only very limited results. For cancers of the digestive system, bladder and brain, there is little evidence of an association with ETS exposure. Some studies have reported a relationship with cancer of the breast, cervix or nasopharynx, but the overall evidence for these sites is inconsistent and inconclusive, as is that for total cancer incidence. All three studies of nasosinus cancer have reported a statistically significant association with ETS exposure, but they are small, control poorly for potential confounding and have other weaknesses. Taken as a whole, the epidemiological evidence provides little support for the view that ETS causes cancer of any of the sites considered.

Pulmonary diseases in women

Pulmonary disease has tremendous impact on both men and women. Fortunately, we have the capacity to prevent a significant percentage of disease with appropriate education for physicians and patients. The majority of the article on pulmonary diseases in women will address smoking and its impact on women's health, as well as smoking cessation. Pulmonary diseases that effect women particularly will be addressed as well.

Cancer incidence in female smokers: a 26-year follow-up

A random sample of 26,000 Swedish women who were asked about their smoking habits in the early 1960s have now been followed for 26 years with respect to cancer incidence. Most findings regarding tobacco smoking and cancer from studies of men were confirmed also among the women. Elevated relative risk for current smokers compared with women who never smoked regularly were seen for cancers of the lung, upper aerodigestive sites, pancreas, bladder, cervix and all cancers combined, as well as a notably high relative risk for cancers of organs of the urinary tract other than kidney and bladder. Relative risk increased with dose, measured as grams of tobacco smoked per day, for cancers of the upper aerodigestive sites, lung, cervix, bladder, organs of the urinary tract other than kidney and bladder and all cancers combined. For cancers of the lung, bladder and cervix, there was an inverse relationship with age when starting to smoke tobacco. The reported inverse relationship between smoking and endometrial cancer could not be corroborated, nor was there any significant relationship between smoking and colorectal or breast cancer.

Overview of the epidemiology of colorectal cancer

INTRODUCTION

The epidemiology of colorectal cancer has generated more interest recently, because recent developments in genetics, molecular biology, and genetic epidemiology have increased our understanding of the role of genes in the etiology of colorectal cancer. Interactions between genetic susceptibility and environmental factors in the etiology of cancer may be easier to define.

EPIDEMIOLOGY

Colorectal cancer is common in the Western world and is rare in developing countries. A sharp increase is seen in Eastern Europe and Japan.

ETIOLOGY

Molecular genetics has shown that accumulation of genetic changes is important in the development of colorectal cancer. Mutations in at least four to five genes are required for the formation of a malignant tumor. Environmental mutagenic factors may determine which susceptible individuals grow carcinomas. Environmental risk factors for colorectal cancer are found in a western diet, rich in fat, meat, and animal protein and low in fiber, fruit, and vegetables. The complex interrelations between food components make it difficult to define the precise role of specific food factors.

PREVENTION

Conclusive evidence of the effectiveness of primary prevention of colorectal cancer via dietary measures or nonsteroidal anti-inflammatory drugs is lacking. Secondary prevention by interrupting the adenoma carcinoma sequence is an actual possibility, its effectiveness, however, needs to be determined. Molecular genetics holds a promise for identifying populations at high risk for colorectal cancer, therefore, targeting the screening to make it more cost-effective.

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.

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.

Subsite-specific risk factors for colorectal cancer: a hospital-based case-control study in Japan

To investigate the subsite-specific risk factors for colorectal cancer, we conducted a case-control study, using a common questionnaire which inquired about general lifestyles over the past five years (1988-92), at the Aichi Cancer Center Hospital, Nagoya, Japan. This study compared 432 patients with histopathologically diagnosed colorectal cancer (94 proximal colon [cecum, ascending colon, transverse colon]; 137 distal colon [descending colon, sigmoid colon]; 201 rectum [rectosigmoid, rectum]); and 31,782 first-visit outpatient controls who were free from cancer. In both genders, habitual smoking selectively increased the risk for rectum cancer. Soft or loose feces increased the risk for all subsites of colorectal cancer, particularly in female rectum cancer (odds ratio [OR] = 4.5). Among female dietary habits, Japanese-style foods decreased the risk for distal colon cancer, but increased the risk for proximal colon cancer. These results suggested that the risk factors for colorectal cancer differ by subsite among such a low-risk population as the Japanese. It is suggested also that 'irritable bowel' (soft or loose feces) might be associated with distal subsites of colorectal cancer, independently or combined with habitual smoking.

Increased risk of colorectal cancer among smokers: results of a 26-year follow-up of US veterans and a review

To clarify the relationship between tobacco use and risk of colorectal cancer, we evaluated a cohort of 248,046 American veterans followed prospectively for 26 years. In comparison with veterans who had never used tobacco, the risk of death was significantly increased for colon cancer and rectal cancer among current and former cigarette smokers and among pipe or cigar smokers, controlling for social class and occupational physical activity. Rectal-cancer risk was also significantly elevated among users of chewing tobacco or snuff. For both sites, risk increased significantly with pack-years, earlier age at first use, and number of cigarettes. These results reinforce 2 recent reports of the association of cigarette smoking and colorectal cancer in men and women. Inconsistencies in the findings of earlier epidemiologic studies appear to be due in large part to differences in length of follow-up or in choice of controls. Studies with at least 20 years of follow-up or population-based controls have tended to find elevated risk with tobacco smoking, while those with shorter follow-up or hospital controls have not. This, plus the strength and consistency of the association of smoking and colon polyps, suggest that smoking may primarily affect an early stage in the development of colon cancer. If this association is causal, tobacco use may be responsible for 16% of colon-cancer and 22% of rectal-cancer deaths among these veterans.

Risk factors for colorectal cancer in patients with ulcerative colitis: a case-control study

BACKGROUND/AIMS

The risk of colorectal cancer increases in patients with ulcerative colitis, most markedly among young patients and/or those with extensive disease at onset. However, it is unknown whether individual risk can be predicted more precisely and whether cancer risk can be reduced by long-term treatment with sulfasalazine.

METHODS

In a population-based cohort of 3112 patients with ulcerative colitis, we compared 102 cases of colorectal cancer and 196 matched controls without cancer. Hospital records were used to abstract information on pharmacological therapy, disease activity, and extraintestinal manifestations. The relative risk (RR) of cancer was estimated by conditional logistic regression.

RESULTS

Pharmacological therapy, especially sulfasalazine, lasting at least 3 months was associated with a significant protective effect (RR, 0.38; 95% confidence interval [CI], 0.20-0.69) independent of disease activity. There was also a tendency to an independent protective effect for cigarette smoking (RR, 0.15; 95% CI, 0.02-1.25) and higher disease activity (RR, 0.80; 95% CI, 0.49-1.33).

CONCLUSIONS

The risk of colorectal cancer among patients with ulcerative colitis can be reduced through pharmacological therapy. This finding is consistent with the reports of a protective effect of aspirin among individuals in the general population.

Cigarette smoking, alcohol, and the risk of colorectal adenomas

BACKGROUND

The present study was designed to further assess the reported association between cigarette smoking, alcohol, and colorectal adenomas.

METHODS

A number of environmental and life-style risk factors were examined in 236 patients with histologically proven adenomas and 409 controls with no adenomas.

RESULTS

Age, sex, race, and indication for procedure were similar in cases and controls. Those who had ever smoked were not at increased risk for adenomas compared with those who had never smoked. Years of smoking, cigarettes per day, and total pack-years showed no dose-response effect. Results for men and women were similar. Alcohol was a significant risk factor for men but not for women. Men in the highest quartile of daily caloric intake from alcohol were more than four times more likely than nondrinkers to develop adenomas, with a statistically significant trend in risk from the lowest to the highest quartile. These findings persisted after controlling for other potential risk factors for adenomas. The risk for colon and rectal polyps were similar. Men in the highest tertile of beer consumption were nearly six times more likely to develop adenomas than nondrinkers.

CONCLUSIONS

Beer drinking is a risk factor for colorectal adenomas in this population.

Environmental tobacco smoke and the risk of cancer in adults

The apparent effect of environmental tobacco smoke (ETS) exposure on cancer risk has become an important social and political issue. The risk of cancer in non-smokers is often the main reason for prohibiting or restricting smoking in public places. A number of epidemiological studies have shown an association between ETS exposure and lung cancer. However, the strength of this association has still to be estimated. Only a few studies have reported on ETS and cancer from sites other than the lung in adults. No definite conclusions can be drawn at present from a critical review of the epidemiological evidence, but the suggestion of an association is present for sinonasal cancer, while bladder cancer does not seem to be associated to ETS exposure. Positive studies are available for cancers from other sites, including the breast, the uterine cervix and the brain, but these are difficult to interpret.

The health consequences of smoking. Cancer

Smoking has now been identified as a definite cause of cancer at many sites (Table 2). Of all cancers in the United States, 30% could be prevented if cigarette smoking were eliminated. Organs in direct contact with smoke--the oral cavity, esophagus, lung, and bronchus--are at the greatest risk of malignancy among smokers. As many as 90% of these cancers are attributable to smoking. Organs and tissues distant from smoke are also at some increased risk. Among smokers, rates of cancer of the cervix, pancreas, bladder, kidney, stomach, and hematopoietic tissue are increased 50% to 200% over rates in nonsmokers. Risk of cancer at all sites increases with increasing exposure to cigarette smoke. Cigarette smoke contains potent carcinogens that influence carcinogenesis at both early and late stages. These carcinogens can interact with other exposures, such as alcohol, to synergistically increase the risk of cancer. The adverse carcinogenic effects of cigarette smoking, however, can be reduced for all smokers if tobacco use is stopped. The prevalence of smoking among the US population as a whole has declined from 40% in 1965 to 29% in 1987. This progress against the epidemic of tobacco use has already produced a decrease in the occurrence of the most common tumor among men, lung cancer. Unfortunately, the decline in smoking prevalence and cancer incidence has not occurred equally across US populations. Death rates of lung cancer in women continue to rise, and, based upon current smoking patterns, these rates will continue to increase into the next century. The challenge to physicians and public health workers is compelling and immediate: Abstaining from smoking is the single most effective way to reduce an individual's risk of cancer.

A prospective study of tobacco use and multiple myeloma: evidence against an association

The relationship between the use of cigarettes and other tobacco products and the risk of multiple myeloma was examined in a cohort of nearly 250,000 American veterans followed prospectively for 26 years. Compared with men who had never tobacco, the risk of death from myeloma was not increased among current (relative risk [RR] = 0.9, 95 percent confidence interval [CI] = 0.8-1.2) or former (RR = 1.0, CI = 0.8-1.3) cigarette smokers, nor among users of chewing tobacco or snuff (RR = 1.0, CI = 0.4-2.3). Risk was only slightly and nonsignificantly increased among pipe or cigar smokers (RR = 1.2, CI = 0.9-1.5). There was no indication of increasing risk with amount of tobacco used or earlier age at first use. With over 90 percent power to detect a 30 percent increased risk of this tumor occurring among current cigarette smokers, this study provides the strongest evidence to date against an association of cigarette smoking with multiple myeloma.

Occupational exposures and cancer of the colon and rectum

The associations between occupational risks and colorectal cancer were examined in a Swedish population-based, case-referent study. The study was performed in Stockholm in 1986-1988 and included 569 cases and 512 referents. Relative risks (RRs) with 95% confidence intervals were calculated for different occupations/chemicals. Elevated risks of colon cancer were found among male petrol station/automobile repair workers (RR = 2.3, 0.8-6.6) and among males exposed to asbestos (RR = 1.8, 0.9-3.6), while elevated risks of rectal cancer were found among males exposed to soot (RR = 2.2, 1.1-4.3), asbestos (RR = 2.2, 1.0-4.7), cutting fluids/oils (RR = 2.1, 1.1-4.0), and combustion gases from coal/coke/wood (RR = 1.9, 1.0-3.7). However, due to a high correlation between the above-mentioned variables and the few exposed subjects, it is difficult to separate their effects properly. These analyses were adjusted for age. Further adjustments for diet, body mass, and physical activity had little or no influence on the results.

Tobacco smoking as a risk factor for colon polyps

BACKGROUND

Data from a cancer screening project among pattern makers were used to evaluate the association between tobacco smoking and prevalence of colon polyps.

METHODS

From 1981-1983, 549 White men were examined by flexible sigmoidoscopy and completed self-administered questionnaires including smoking histories.

RESULTS

One or more colon polyps were detected in 76 men. Standardized prevalence rates (SPR) for polyps increased by smoking category (never smoked = 0.094; ex-smokers = 0.118, current smokers = 0.214) and by cigarettes per day, years of smoking, and pack-years among both current and ex-smokers. Both adenomatous and hyperplastic polyps showed an association with smoking while other types of polyps and polyps with unspecified histology did not. The risk associated with smoking was greater for polyps greater than one centimeter in diameter. An interaction with occupational exposures was suggested by a greater increase in the SPR for polyps among current smokers employed as pattern makers for more than 10 years than among current smokers similarly employed for 10 years or less.

CONCLUSIONS

Since at least some colon polyps are considered precursor lesions to colon cancer, one of the most common cancers in the United States, this report suggests that the possible link between colon polyps and smoking deserves further evaluation.

A prospective study of body mass, height, and smoking on the risk of colorectal cancer in women

Female registered nurses in the United States who responded to a questionnaire in 1976 that inquired about height, weight, and smoking history were followed for the development of colon or rectal cancers through May of 1984. Among the 118,404 respondents free of cancer in 1976, 191 colon cancers and 49 rectal cancers were observed during 916,170 person-years of follow-up. After omitting cases diagnosed within two years of weight report, we found little overall relation of body mass (Quetelet's) index to colon cancer risk; however there was a suggestion of elevated risk for the heaviest category of body mass index (greater than or equal to 29 kg/m2, relative risk (RR) = 1.5; 95 percent confidence interval = 0.8 - 2.7) relative to the lowest category (less than 21 kg/m2). Self-reported body mass index from adolescence had a slightly more pronounced, although not significant, association with risk of colon cancer. Increasing height was significantly associated with colon cancer (RR = 1.6, 95 percent confidence interval = 1.1 - 2.5 for the tallest category [greater than or equal to 168 cm] versus the shortest (less than 160 cm], trend, P = 0.04). Measures of current or past smoking failed to demonstrate any consistent relationship with colon cancer.

Natural history of colorectal polyps and the effect of polypectomy on occurrence of subsequent cancer

To elucidate the natural history of colorectal polyps and to observe the influence of endoscopic polypectomy on the incidence of colorectal cancer, we conducted a retrospective cohort study of all patients who had undergone colonoscopic examination at the Center for Adult Diseases, Osaka, between April 1974 and December 1985. The study subjects consisted of a control group (760 non-polyp patients) and a polyp group (648 polyp patients, including 136 treated by polypectomy at the initial examination). These subjects were followed up until the end of 1987 by record linkage with the Osaka Cancer Registry's file to observe the occurrence of colorectal cancer. The O/E (observed/expected numbers derived from the general population) was 5.1 (95% confidence interval = 2.5-9.4) and 1.0 (0.1-3.6) for the polyp and control group, respectively. When subjects in the polyp group were categorized into polypectomy and non-polypectomy sub-groups, the O/E was 2.3 (0.1-12.6) and 8.0 (3.4-15.8) respectively. The relative risk of undergoing polypectomy to developing subsequent cancer was estimated at 0.3 (0.1-2.1). These results suggest an increased risk of developing cancer among polyp patients and the possibility of prophylactic effect of polypectomy against subsequent cancer. A large-scale and long-term follow-up study is required to confirm these findings.

A case-control study of male colorectal cancer in Aichi Prefecture, Japan: with special reference to occupational activity level, drinking habits and family history

The relationships of occupational activity level, drinking habits and family history of cancer to the risk of male colorectal cancer by subsites were investigated in a case-control study involving 1,716 cases with colon cancer, 1,611 cases with rectal cancer and 16,600 controls with other sites of cancer identified from the Aichi Cancer Registry, Japan 1979-1987. An occupation with a low activity level was associated with an increased risk of colorectal cancer; the age-adjusted relative risk (RR) compared to the high activity level group was 1.92 (95% confidence interval (CI): 1.38-2.67) for proximal colon cancer, 1.52 (95% CI: 1.19-1.94) for distal colon cancer and 1.38 (95% CI: 1.17-1.62) for rectal cancer. Beer drinkers showed an increased risk of colorectal cancer; the age-adjusted RR was 1.49 (95% CI: 1.13-1.95) for proximal colon cancer, 1.65 (95% CI: 1.34-2.04) for distal colon cancer and 1.88 (95% CI: 1.62-2.18) for rectal cancer. The RR for family history of colorectal cancer was 3.40 (95% CI: 2.19-5.29) for proximal colon cancer, 2.54 (95% CI: 1.73-3.75) for distal colon cancer and 1.78 (95% CI: 1.28-2.49) for rectal cancer. Multivariate analysis controlled for age, residence, marital status and smoking in addition to occupational activity level, beer drinking and family history of colorectal cancer did not materially change the RRs. When these three variables were combined, the RR was 15.72 (95% CI: 5.40-45.78) for proximal colon cancer, 10.55 (95% CI: 4.24-26.27) for distal colon cancer and 6.69 (95% CI: 3.12-14.36) for rectal cancer.