National Enhanced Cancer Surveillance System Research Articles

Ambient polycyclic aromatic hydrocarbon exposure and breast cancer risk in a population-based Canadian case–control study

PurposePolycyclic aromatic hydrocarbons (PAHs) represent a class of ubiquitous pollutants recognized as established human carcinogens and endocrine-disrupting chemicals. PAHs have seldom been modeled at the population-level in epidemiological studies. Fluoranthene is a prevalent PAH in urban settings and correlates with the occurrence of other PAHs. The purpose of this study was to evaluate associations between long-term residential exposure to ambient PAHs and breast cancer risk, both pre- and post-menopausal, in Canada.MethodsUsing the National Enhanced Cancer Surveillance System (NECSS), a national-scale Canadian population-based case–control study, annual fluoranthene exposures were estimated using the GEM-MACH-PAH chemical transport model on the basis of geocoded residential histories throughout a 20-year exposure window. Odds ratios (ORs) and 95% confidence intervals (CIs) controlling for potential confounders were estimated using logistic regression. Separate analyses were conducted for Ontario and national samples given a finer-resolution exposure surface and additional risk factor information available for Ontario.ResultsPositive associations were observed between fluoranthene exposure and premenopausal breast cancer, with inconsistent findings for postmenopausal breast cancer. For premenopausal breast cancer, adjusted ORs of 2.48 (95% CI: 1.29, 4.77) and 1.59 (95% CI: 1.11, 2.29) were observed when comparing the second highest category of exposure to the lowest, among the Ontario and national samples, respectively. For postmenopausal breast cancer, adjusted ORs were 1.10 (95% CI: 0.67, 1.80) and 1.33 (95% CI: 1.02, 1.73). Associations for the highest level of exposure, across both samples and menopausal strata, were non-significant.ConclusionThis study provides support for the hypothesis that ambient PAH exposures increase the risk of premenopausal breast cancer.

Silica and asbestos exposure at work and the risk of bladder cancer in Canadian men: a population-based case-control study

BackgroundSilica and asbestos are recognized lung carcinogens. However, their role in carcinogenesis at other organs is less clear. Clearance of inhaled silica particles and asbestos fibers from the lungs may lead to translocation to sites such as the bladder where they may initiate carcinogenesis. We used data from a Canadian population-based case-control study to evaluate the associations between these workplace exposures and bladder cancer.MethodsData from a population-based case-control study were used to characterize associations between workplace exposure to silica and asbestos and bladder cancer among men. Bladder cancer cases (N = 658) and age-frequency matched controls (N = 1360) were recruited within the National Enhanced Cancer Surveillance System from eight Canadian provinces (1994–97). Exposure concentration, frequency and reliability for silica and asbestos were assigned to each job, based on lifetime occupational histories, using a combination of job-exposure profiles and expert review. Exposure was modeled as ever/never, highest attained concentration, duration (years), highest attained frequency (% worktime) and cumulative exposure. Odds ratios (OR) and their 95% confidence intervals (CI) were estimated using adjusted logistic regression.ResultsA modest (approximately 20%) increase in bladder cancer risk was found for ever having been exposed to silica, highest attained concentration and frequency of exposure but this increase was not statistically significant. Relative to unexposed, the odds of bladder cancer were 1.41 (95%CI: 1.01–1.98) times higher among men exposed to silica at work for ≥27 years. For asbestos, relative to unexposed, an increased risk of bladder cancer was observed for those first exposed ≥20 years ago (OR:2.04, 95%CI:1.25–3.34), those with a frequency of exposure of 5–30% of worktime (OR:1.45, 95%CI:1.06–1.98), and for those with < 10 years of exposure at low concentrations (OR:1.75, 95%CI:1.10–2.77) and the lower tertile of cumulative exposure (OR:1.69, 95%CI:1.07–2.65). However, no clear exposure-response relationships emerged.ConclusionsOur results indicate a slight increase in risk of bladder cancer with exposure to silica and asbestos, suggesting that the effects of these agents are broader than currently recognized. The findings from this study inform evidence-based action to enhance cancer prevention efforts, particularly for workers in industries with regular exposure.

Workplace exposure to asbestos and the risk of kidney cancer in Canadian men

ObjectivePrevious studies considered the role of occupational causes in kidney cancer but were limited by small sample sizes and imprecise exposure assessment. This study examined the relationship between occupational exposure to asbestos and the risk of kidney cancer across a range of jobs in a large, population-based case-control study in Canada.MethodsData were from the case-control component of the National Enhanced Cancer Surveillance System, a study conducted between 1994 and 1997 in eight Canadian provinces. Male kidney cancer cases, histologically confirmed, and controls completed questionnaires on socio-demographics, anthropometry, diet, smoking, secondhand smoke exposure, and physical activity. Occupational histories were also collected, including each job held for at least 1 year since the age of 18. Occupational hygienists, blinded to case status, assigned exposure to asbestos, considering intensity, frequency, and probability of exposure (each 3-point scales). Logistic regression was used to estimate the odds of kidney cancer in exposed participants (defined using three metrics) compared to those without asbestos exposure.ResultsThere were 712 cases and 2454 controls in these analyses. Ever-exposure to asbestos was associated with 20% increased odds of kidney cancer compared to unexposed workers (OR 1.2, 95% confidence interval 1.0–1.4 when including possibly exposed workers). A small increase in risk was observed with cumulative exposure, while increasing intensity of exposure was related to increased odds of kidney cancer.ConclusionsThis study found some evidence for an association between occupational exposure to asbestos and kidney cancer. Higher intensity of exposure to asbestos had the strongest relationship with kidney cancer risk.

Occupational Exposure to Diesel and Gasoline Engine Exhausts and the Risk of Kidney Cancer in Canadian Men.

IntroductionKidney cancer is the fifth most common incident cancer in Canadian men. Diesel and gasoline exhausts are common workplace exposures that have been examined as risk factors for non-lung cancer sites, including the kidney, but limitations in exposure assessment methods have contributed to inconsistent findings. The objective of this study was to assess the relationship between occupational gasoline and diesel engine exhausts and the risk of kidney cancer in men.MethodsThe National Enhanced Cancer Surveillance System (NECSS) is a Canadian population-based case–control study conducted in 1994–1997. Incident kidney cancer cases were identified using provincial registries, while the control series was identified through random-digit dialing, or provincial administrative databases. Self-reported questionnaires were used to obtain information on lifetime occupational history and cancer risk factors. Two hygienists, blinded to case status, coded occupational histories for diesel and gasoline exhaust exposures using concentration, frequency, duration, and reliability. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) separately by exhaust type. The separate and combined impacts of both engine exhausts were also examined. ORs were adjusted for age, province, body mass index, occupational secondhand smoke exposure, and education.ResultsOf the kidney cancer cases (n = 712), 372 (52%) had exposure to both exhausts at some point, and 984 (40%) of the controls (n = 2457) were ever exposed. Workers who had ever been exposed to engine exhausts were more likely to have kidney cancer than those who were never exposed (OR diesel = 1.23, 95% CI = 0.99–1.53; OR gasoline = 1.51, 95% CI = 1.23–1.86). Exposure to gasoline exhaust was consistently associated with kidney cancer in a dose–response manner (P value for trends in highest attained and cumulative exposure both <0.0001). Those men with high cumulative exposure to both gasoline and diesel exhaust had a 76% increased odds of kidney cancer (95% CI = 1.27–2.43).ConclusionsThis study provides evidence that occupational gasoline, and to a lesser extent, diesel exhaust exposure may increase the risk of kidney cancer.

Is there link between occupational physical activity levels and lung cancer? A case-control study in Canadian men

Background/Aim Many studies have looked at the association between daily physical activity levels and risk of lung cancer, but very little research has been conducted where occupational physical activity (OPA) levels are isolated from recreational physical activity levels. As Canadian jobs are becoming increasingly sedentary, and Canadians spend roughly 50% of their waking day at work, this is a concern. The purpose of this study was to determine whether a link exists between occupational physical activity levels and risk of lung cancer in Canadian men. Methods This study used National Enhanced Cancer Surveillance System (NECSS) data, a questionnaire-based case-control study conducted across eight Canadian provinces between 1994 and 1997. Cases of lung cancer were identified using provincial cancer registries and controls were selected from a random sample from the same province and with a similar age and sex distribution as that of the cancer cases. Occupational physical activity levels were defined by the Canadian Classification and Dictionary of Occupations (CCDO), which includes ancillary information on occupational physical activity scores in categories of sedentary, light, moderate, heavy, and very heavy physical activity. Analysis was conducted using last job held. Basic descriptive statistics were calculated to compare cases and controls as part of a preliminary analysis. SAS software was used to fit categorical linear models to the response frequencies. Results The NECSS data includes information on 1682 male lung cancer cases and 2054 male controls. For analysis purposes very heavy OPA and heavy OPA were combined due to small sample sizes. Overall, workers fell into four categories; heavy OPA (16%), moderate OPA (35%), light OPA (31%), and sedentary OPA (17%). The remaining 1% of workers had unknown OPA and were excluded from further analysis. Further stratification for smoking status showed similar distributions across OPA categories. Of cases who never smoked, 2% worked heavy OPA jobs, 1% worked moderate OPA jobs, 3% worked light OPA jobs, and 3% worked sedentary OPA jobs. Of cases who are ex-smokers 80% worked heavy OPA jobs, 80% worked moderate OPA jobs, 80% worked light OPA jobs, and 83% worked sedentary OPA jobs. Of cases who currently smoke, 18% worked heavy OPA jobs, 19% worked moderate OPA jobs, 17% worked light OPA jobs, and 14% worked sedentary OPA jobs. A main effects model yielded statistically significant results for OPA (P Conclusion We found some evidence that occupational physical activity levels are associated with an increased risk of lung cancer among Canadian males. Further analyses should consider other covariates and modelling interactions.

Is There a Link between Occupational Silica or Asbestos Exposure and Kidney Cancer? A Case-Control Study in Canadian men

Background/Aim: Asbestos and crystalline silica are prevalent workplace exposures and are recognized human carcinogens. As few studies have investigated their associations with kidney cancer, we sought to address this gap using a Canadian case-control study. Methods: Incident cancer cases were identified by provincial cancer registries and self-reported questionnaires were used to obtain information on cancer risk factors and lifetime occupational history as part of the National Enhanced Cancer Surveillance System (NECSS). The NECSS is a population-based case-control study conducted from 1994-1997 in eight Canadian provinces. Occupational hygienists coded occupational histories for asbestos and silica exposure using concentration, frequency, and reliability, enabling the development of several exposure metrics. Logistic regression was used to estimate, separately by exposure, odds ratios (OR) and 95% confidence intervals. Models were adjusted for age, province, BMI, and cigarette smoking. Results: Complete occupational data were available for 652 cancer cases and 2,368 controls. Overall, 33% and 44% of workers were ever occupationally exposed to asbestos and silica, respectively. Obesity and older age were positively associated with kidney cancer, however smoking was not. Workers who had ever been exposed to asbestos were significantly more likely to have kidney cancer than those who were never exposed (OR 1.2, 95% CI 1.0 – 1.5). Ever-exposure to silica was not related to a significantly elevated risk of kidney cancer (OR 1.1, 95%CI 0.9 – 1.4). When examining duration of exposure as well as tertiles of cumulative asbestos exposure, calculated by multiplying relative frequency and concentration by duration, exposure was linked to an increased risk of kidney cancer, but only significantly so in the lowest tertile (OR 1.4, 1.0 – 1.9). In similar analyses for silica, no significant relationships were observed when comparing exposed to unexposed workers. Conclusions: We found evidence that occupational exposure to asbestos, but not silica, is positively associated with kidney cancer.

Occupation and risk of prostate cancer in Canadian men: A case-control study across eight Canadian provinces

BackgroundThe etiology of prostate cancer continues to be poorly understood, including the role of occupation. Past Canadian studies have not been able to thoroughly examine prostate cancer by occupation with detailed information on individual level factors. MethodsOccupation, industry and prostate cancer were examined using data from the National Enhanced Cancer Surveillance System, a large population-based case-control study conducted across eight Canadian provinces from 1994 to 1997. This analysis included 1737 incident cases and 1803 controls aged 50 to 79 years. Lifetime occupational histories were used to group individuals by occupation and industry employment. Odds ratios and 95% confidence intervals were calculated and adjustments were made for known and possible risk factors. ResultsBy occupation, elevated risks were observed in farming and farm management (OR=1.37, 95% CI 1.02–1.84), armed forces (OR=1.33, 95% CI 1.06-1.65) and legal work (OR=2.58, 95% CI 1.05–6.35). Elevated risks were also observed in office work (OR=1.20, 95% CI 1.00–1.43) and plumbing (OR=1.77, 95% CI 1.07–2.93) and with ≥10 years duration of employment. Decreased risks were observed in senior management (OR=0.65, 95% CI 0.46–0.91), construction management (OR=0.69, 95% CI 0.50–0.94) and travel work (OR=0.37, 95% CI 0.16–0.88). Industry results were similar to occupation results, except for an elevated risk in forestry/logging (OR=1.54, 95% CI 1.06–2.25) and a decreased risk in primary metal products (OR=0.70, 95% CI 0.51–0.96). ConclusionThis study presents associations between occupation, industry and prostate cancer, while accounting for individual level factors. Further research is needed on potential job-specific exposures and screening behaviours.

Occupational exposure to magnetic fields and breast cancer among Canadian men.

Occupational magnetic field (MF) exposure has been suggested as a risk factor for breast cancer in both men and women. Due to the rarity of this disease in men, most epidemiologic studies investigating this relationship have been limited by small sample sizes. Herein, associations of several measures of occupational MF exposure with breast cancer in men were investigated using data from the population‐based case–control component of the Canadian National Enhanced Cancer Surveillance System. Lifetime job histories were provided by 115 cases and 570 controls. Average MF exposure of individual jobs was classified into three categories (<0.3, 0.3 to <0.6, or ≥0.6 μT) through expert blinded review of participant's lifetime occupational histories. The impact of highest average and cumulative MF exposure, as well as exposure duration and specific exposure‐time windows, on cancer risk was examined using logistic regression. The proportion of cases (25%) with a highest average exposure of ≥0.3 μT was higher than among controls (22%). We found an elevated risk of breast cancer in men who were exposed to ≥0.6 μT (odds ratio [OR] = 1.80, 95% CI = 0.82–3.95) when compared to those with exposures <0.3 μT. Those exposed to occupational MF fields for at least 30 years had a nearly threefold increase in risk of breast cancer (OR = 2.77, 95% CI = 0.98–7.82) when compared to those with background levels of exposure. Findings for the other time‐related MF variables were inconsistent. Our analysis, in one of the largest case–control studies of breast cancer in men conducted to date, provides limited support for the hypothesis that exposure to MF increases the risk breast cancer in men.

Dietary patterns and the risk of female breast cancer among participants of the Canadian National Enhanced Cancer Surveillance System.

The role of diet in the etiology of breast cancer is not well understood despite extensive research. In the majority of this work, a single nutrient-based approach has been used which does not take into account combinations of food that are consumed. An alternative to the single nutrient approach is to identify patterns in the dietary intake information and relate these patterns to disease incidence. This investigation characterized dietary patterns among participants of a Canadian case-control study and related these dietary patterns to the incidence of breast cancer. Dietary and other risk factor data from cases and controls of the Canadian National Enhanced Cancer Surveillance System were collected using self-administered questionnaires. Principal component factor analysis was used to classify individuals based on their dietary patterns. The relationship between these dietary patterns and breast cancer was evaluated using logistic regression. The derived odds ratios and their 95% confidence limits were adjusted for several factors, such as smoking, alcohol intake, environmental tobacco smoke exposure and obesity. In the 2,009 cases and 2,086 controls, three dietary patterns were identified: western, healthy and vitamin. The highest quartile of the "healthy" dietary pattern was related to a 22% decrease in breast cancer risk (95% CI: 0.61-1.00), relative to the lowest quartile. The fourth quartile of the "vitamin" dietary pattern was associated with a 14% decrease in breast cancer risk (95% CI: 0.70-1.04) relative to the first. No statistically significant associations between the "western" dietary pattern and breast cancer were found. These associations were neither confounded nor modified by menopausal status. Our analyses reveal that individual dietary items tend to cluster together in such a way that there are three distinct dietary patterns in this sample of Canadian women. Some of these patterns, in turn, were associated with the risk of breast cancer.

Bladder cancer and occupational exposure to diesel and gasoline engine emissions among Canadian men.

The International Agency for Research on Cancer has classified diesel exhaust as a carcinogen based on lung cancer evidence; however, few studies have investigated the effect of engine emissions on bladder cancer. The purpose of this study was to investigate the association between occupational exposure to diesel and gasoline emissions and bladder cancer in men using data from the Canadian National Enhanced Cancer Surveillance System; a population‐based case–control study. This analysis included 658 bladder cancer cases and 1360 controls with information on lifetime occupational histories and a large number of possible cancer risk factors. A job‐exposure matrix for engine emissions was supplemented by expert review to assign values for each job across three dimensions of exposure: concentration, frequency, and reliability. Odds ratios (OR) and their corresponding 95% confidence intervals were estimated using logistic regression. Relative to unexposed, men ever exposed to high concentrations of diesel emissions were at an increased risk of bladder cancer (OR = 1.64, 0.87–3.08), but this result was not significant, and those with >10 years of exposure to diesel emissions at high concentrations had a greater than twofold increase in risk (OR = 2.45, 1.04–5.74). Increased risk of bladder cancer was also observed with >30% of work time exposed to gasoline engine emissions (OR = 1.59, 1.04–2.43) relative to the unexposed, but only among men that had never been exposed to diesel emissions. Taken together, our findings support the hypothesis that exposure to high concentrations of diesel engine emissions may increase the risk of bladder cancer.

Exposure to traffic-related air pollution and the risk of developing breast cancer among women in eight Canadian provinces: A case–control study

A few recent studies have reported positive associations between long-term exposure to traffic-related air pollution and the incidence of breast cancer. We capitalized on an existing Canadian multi-site population-based case–control study to further investigate this association.We used the National Enhanced Cancer Surveillance System, a population-based case–control study conducted in eight of 10 Canadian provinces from 1994 to 1997. A total of 1569 breast cancer cases and 1872 population controls who reported at least 90% complete self-reported addresses over the 1975–1994 exposure period were examined. Mean exposure levels to nitrogen dioxide (NO2) (an indicator of traffic-related air pollution) were estimated for this period using three different measures: (1) satellite-derived observations; (2) satellite-derived observations scaled with historical fixed-site measurements of NO2; and (3) a national land-use regression (LUR) model. Proximity to major roads was also examined. Using unconditional logistic regression, stratified by menopausal status, we estimated odds ratios (ORs) adjusted for many individual-level and contextual breast cancer risk factors.We observed positive associations between incident breast cancer and all three measures of NO2 exposure from 1975 to 1994. In fully adjusted models for premenopausal breast cancer, a 10ppb increase in NO2 exposure estimated from the satellite-derived observations, the scaled satellite-derived observations, and the national LUR model produced ORs of 1.26 (95% confidence intervals (CIs): 0.92–1.74), 1.32 (95% CI: 1.05–1.67) and 1.28 (95% CI: 0.92–1.79). For postmenopausal breast cancer, we found corresponding ORs of 1.10 (95% CI: 0.88–1.36), 1.10 (95% CI: 0.94–1.28) and 1.07 (95% CI: 0.86–1.32). Substantial heterogeneity in the ORs was observed across the eight Canadian provinces and reduced ORs were observed when models were restricted to women who had received routine mammography examinations. No associations were found for road proximity measures.This study provides some support for the hypothesis that traffic-related air pollution may be associated with the development of breast cancer, especially in premenopausal women. With the few studies available, further research is clearly needed.

Exploring Associations between Traffic-Related Air Pollution and Female Breast and Prostate Cancer using a Multi-Site Population-Based Case-Control Study in Can

Background: Recent studies have reported positive associations between exposure to traffic-related air pollution and breast and prostate cancer incidence; however, few studies have been conducted and the findings are mixed. Methods: We used the National Enhanced Cancer Surveillance System, a population-based case-control study conducted in 8 of 10 Canadian provinces from 1994 to 1997. Our analyses are based on 1,829 post-menopausal incident breast cancer cases and 2,432 female controls, and 1,763 incident prostate cancer cases and 2,477 male controls. Residential histories over a 20 year period were used with a geographic information system to estimate urbanicity, population density, and road proximity measures. Long-term nitrogen dioxide (NO2) exposure measures were estimated from fixed-site air pollution monitors as well as spatiotemporal modeling methods. We calculated odds ratios (ORs) using logistic regression and adjusted for several known and suspected risk factors from self-reported questionnaires for each cancer site. Results: Preliminary analyses showed no consistent associations between breast cancer and long-term exposure measures, including years residing in large urban areas, average population density within 1, 5 and 10 km's of residences, proximity to major roads, and measured and modelled NO2 exposure. For example, the odds of breast cancer associated with a 10 ppb increase in modelled NO2 exposure was 1.07 (95% CI: 0.88-1.28). Similarly for prostate cancer, no associations were observed with years residing in large urban areas and average population density within 1, 5 and 10 km's of residences. Increased associations were observed for prostate cancer and 10 ppb increases in measured (OR: 1.11; 95% CI: 0.92-1.33) and modelled (OR: 1.12; 95% CI: 0.96-1.31) NO2, although the results varied by province. Conclusions: No consistent associations were observed between traffic-related air pollution measures and post-menopausal breast cancer incidence, while some evidence was seen for increased associations for prostate cancer incidence.

Occupational exposures and lung cancer risk by histological type in Canada

ObjectivesTo examine the associations between self-reported occupational exposures and lung cancer risk by histological type in Canada.MethodsWe utilise the lung cancer component of the National Enhanced Cancer Surveillance System, which...

Regarding “Menstrual and Reproductive Risk Factors and Risk for Gastric Adenocarcinoma in Women: Findings from the Canadian National Enhanced Cancer Surveillance System”

Regarding “Menstrual and Reproductive Risk Factors and Risk for Gastric Adenocarcinoma in Women: Findings from the Canadian National Enhanced Cancer Surveillance System”

Menstrual and Reproductive Risk Factors and Risk for Gastric Adenocarcinoma in Women: Findings From the Canadian National Enhanced Cancer Surveillance System

The role of menstrual and reproductive risk factors for gastric cancer has not been well studied. This population-based case-control study included 326 women aged 20 to 74 years with gastric adenocarcinoma. Controls were 326 women frequency matched on age. Data for reproductive and/or hormonal exposure and gastric cancer risk factors were captured through self-administered questionnaire. Later age at menarche was associated with increased risk for adenocarcinoma compared with menarche onset at younger than 13 years of age (13 to 14 years: odds ratio [OR], 1.45; 95% confidence interval [CI], 1.00-2.10; > or =15 years: OR, 1.93; 95% CI, 1.19-3.13). Compared with premenopause, natural menopause was associated with increased risk for adenocarcinoma (OR, 1.99; 95% CI, 0.98-4.05). Compared with nulliparity, 4 or more births were associated with decreased risk for gastric cancer, as was being pregnant for 5 months or longer if the first pregnancy occurred at younger than 24 years (OR, 0.55; 95% CI, 0.31-0.96) or 25 years or older (OR, 0.67; 95% CI, 0.38-1.18). Oral contraceptives and hormone replacement therapy were associated with a non-statistically significant decreased risk. These findings suggest that hormonal factors associated with greater exposure to estrogen and/or progesterone may be associated with decreased risk for gastric cancer.

In this issue

In this issue

Passive and active smoking and breast cancer risk in Canada, 1994-97.

Studies comparing ever smokers with never smokers have found little increase in breast cancer risk. However, the five published studies examining passive smoking and breast cancer have all suggested associations with both passive and active smoking, particularly premenopausal risk. We analyzed data collected through the Canadian National Enhanced Cancer Surveillance System, from 805 premenopausal and 1512 postmenopausal women with newly diagnosed (incident), histologically confirmed, primary breast cancer and 2438 population controls. The mailed questionnaire included questions on breast cancer risk factors and a lifetime residential and occupational history of exposure to passive smoking. Among premenopausal women who were never active smokers, regular exposure to passive smoke was associated with an adjusted breast cancer odds ratio (OR) of 2.3 (95% confidence interval [CI] 1.2-4.6). Passive exposure showed a strong dose-response trend (test for trend p = 0.0007) with an OR of 2.9 (95% CI 1.3-6.6) for more than 35 years of passive residential and/or occupational exposure. When premenopausal women who had ever actively smoked were compared with women never regularly exposed to passive or active smoke, the adjusted OR for breast cancer was also 2.3 (95% CI 1.2-4.5). Among postmenopausal women who were never-active smokers, regular exposure to passive smoke was associated with an adjusted breast cancer OR of 1.2 (95% CI 0.8-1.8) and an OR of 1.4 (95% CI 0.9-2.3) for the most highly exposed quartile of women. The adjusted OR for postmenopausal breast cancer risk for ever-active smokers compared with women never regularly exposed to passive or active smoke was 1.5 (95% CI 1.0-2.3). Statistically significant dose-response relationships were observed with increasing years of smoking, increasing pack-years and decreasing years since quitting. Women with 35 or more years of smoking had an adjusted OR of 1.7 (95% CI 1.1-2.7). Active and passive smoking may be associated with increased breast cancer risk, particularly premenopausal risk.

Risk factors for prostate cancer: results from the Canadian National Enhanced Cancer Surveillance System. The Canadian Cancer Registries Epidemiology Research Group.

To evaluate the relationship between prostate cancer and several potential lifestyle risk factors. We analyzed data obtained from a population-based case-control study conducted in eight Canadian provinces. Risk estimates were generated by applying multivariate logistic regression methods to 1623 histologically confirmed prostate cancer cases and 1623 male controls aged 50-74. Cases were more likely to have a first-degree relative with a history of cancer, particularly prostate cancer (OR = 3.1, 95% CI = 1.8-5.4). Reduced risks of prostate cancer were observed among those of Indian descent (OR = 0.2, 95% CI = 0.1-0.5) or any Asian descent (OR = 0.3, 95% CI = 0.2-0.6) relative to those of western European descent. Total fat consumption, tomato and energy intake, were not associated with prostate cancer. The risk of prostate cancer was inversely related to the number of cigarettes smoked daily (p = 0.06) and cigarette pack-years (p < 0.01), while no association was observed between the total number of smoking years or the number of years since smoking cessation. Anthropometric measures and moderate and strenuous levels of leisure time physical activity were not strongly related to prostate cancer. In contrast, strenuous occupational activities at younger ages appeared protective. Our analyses are limited by the absence of data related to tumor severity and screening history. Further studies are needed to investigate the relationship between behavioral risk factors and prostate cancer screening practices.

The National Enhanced Cancer Surveillance System: a case-control approach to environment-related cancer surveillance in Canada

This paper describes the rationale and basic design of the National Enhanced Cancer Surveillance System. The system is designed to facilitate timely, systematic evaluation of environment-cancer concerns and strengthen cancer surveillance in Canada. There are three key activities: (1) National community-level environmental quality database: The database, created by Health Canada, includes systematic, easily accessible, community-level information on air and water quality. Information includes a national inventory of municipal waste disposal sites, municipal drinking water data, air quality data, historic industrial location and productivity data. (2) Case-control surveillance: The Provincial Cancer Registries are collecting individual data from a large, Canada-wide, population-based series of newly-diagnosed cancer cases for 18 types of cancer and a population control group. Mailed questionnaires and telephone follow-up are used to gather data on residential and occupational histories, diet, physical activity and other risk factors for cancer. Data for over 20,000 cancer cases and 5000 controls have been assembled between 1994 and 1997. The cancer and population control data are being linked to the environmental database to facilitate systematic, community level, case-control assessment of cancer risk related to air and water quality. (3) Geographic surveillance network: Areas of high and/or unusual patterns of cancer incidence are being examined through temporal and spatial mapping, cluster analysis and risk factor evaluation. © 1998 John Wiley & Sons, Ltd.