Fasting insulin and endogenous hormones in relation to premenopausal breast density (Canada).

PURPOSE: Mammographic breast density (BD) is associated with increased risk of breast cancer. This study asks which circulating metabolic and reproductive biomarkers are associated with BD, particularly dense breast area, in premenopausal women not taking exogenous hormones. METHODS: In a cross-sectional study, 299 premenopausal women aged 40-49 completed questionnaires, provided a fasting blood sample, had height, weight, percentage body fat, waist and hip measurements taken, and attended a screening mammogram. Multivariate linear regression was used to calculate adjusted means for percentage BD, absolute dense and non-dense area, across categories of covariates, adjusted for day of menstrual cycle, age, parity, body mass index, percentage body fat, and ethnicity. RESULTS: Fasting insulin levels were inversely associated, and insulin-like growth factor-binding protein 1 levels directly associated with percentage BD, but lost statistical significance after multivariate adjustment. Sex hormone-binding globulin levels were directly associated with percentage BD, still significant after multivariate adjustment (p = 0.03). A significant inverse dose-response association was observed between progesterone levels and dense area (p < 0.01). CONCLUSIONS: Breast density in premenopausal women seems unrelated or inversely related to insulin resistance, levels of insulin-like growth factor 1 and its binding proteins, and levels of sex steroids; therefore, the mechanism by which radiodensity on a mammogram is related to breast cancer risk remains unclear.

Persistent organic pollutants and risk of cutaneous malignant melanoma among women.

BACKGROUND: Despite the increasing trend of cutaneous malignant melanoma (CMM) incidence in Canada, especially among females, few risk factors other than ultraviolet radiation exposure, have been identified. AIM: We conducted a case-control study of 406 CMM cases and 181 controls to evaluate the potential impact of body burdens of various persistent organic pollutants on CMM risk. METHODS: Detailed data on potential confounding factors, including lifetime repeated sun exposure and skin reaction to repeated sun exposure, were collected. Gas chromatography tandem mass spectrometry was used to assay plasma levels of 14 polychlorinated biphenyl (PCB) congeners and 11 organochlorine (OC) pesticides among cases and controls. RESULTS: Statistically significant trends of increased CMM risk were observed with increasing plasma concentrations of multiple PCB congeners, including PCBs 138, 153, 170, 180, 183 and 187. For example, compared to lowest plasma concentration quartile of PCB-138, the second, third and fourth quartiles were associated with 1.7 (95% CI: 0.9-2.9), 2.3 (95% CI: 1.3-4.1) and 2.4 (95% CI: 1.3-4.5) -fold increased risks of CMM, respectively. Similarly, increasing plasma concentrations of several OC pesticides (i.e., ß-HCH, HCB, Mirex, oxychlordane and trans-Nonachlor) showed statistically significant trends with increased CMM risk. For example, compared to lowest plasma concentration quartile of ß-HCH, the second, third and fourth quartiles were associated with 1.3 (95% CI: 0.7-2.3), 2.1 (95% CI: 1.2-3.7) and 2.3 (95% CI: 1.2-4.4) -fold increased risks of CMM, respectively. CONCLUSION: Plasma levels of several persistent organic pollutants were highly correlated, suggesting that observed associations were not necessarily independent of each other. Given the highly correlated nature of exposure to PCB and OC analytes, sophisticated analyses that consider complex mixtures should be considered in future studies.

Plasma levels of polychlorinated biphenyls and risk of cutaneous malignant melanoma: a preliminary study.

A number of epidemiologic studies have suggested that exposure to polychlorinated biphenyls (PCB) and other organochlorine compounds (OCC) increase risk of cutaneous malignant melanoma (CMM). However, these studies have generally had no biologic measure of OCC exposure, and have been unable to control for sun exposure, the major known environmental risk factor for this disease. This preliminary study examined the relationship between OCC residues in plasma and risk of CMM adjusting for sun sensitivity and sun exposure. A case-control study of 80 CMM patients and 310 control subjects was conducted. Lifetime sun exposure information, along with data on pigmentation variables and sun sensitivity data was collected, along with a blood sample. Cases and controls were assayed for plasma levels of 14 PCB congeners and 11 organochlorine pesticide residues using gas chromatography. Strong associations were seen between risk of CMM and plasma levels of non-dioxin-like PCBs (Adjusted OR = 7.02; 95% CI: 2.30-21.43 for highest quartile) and several PCB congeners, organochlorine pesticides or metabolites. These associations persisted after control for sun sensitivity and sun exposure. Results from this investigation require independent confirmation in larger studies. However, they suggest that environmental factors other than UV radiation may play a role in genesis of CMM, and indicate that it may be productive to search for further agents which might increase risk.

Prostate cancer risk and exposure to pesticides in British Columbia farmers.

BACKGROUND: Several epidemiologic studies have reported an increased risk of prostate cancer among farmers. Our aim was to assess the risk of developing prostate cancer in relation to exposure to specific active compounds in pesticides. METHOD: A case-control approach was used with 1,516 prostate cancer patients and 4,994 age-matched internal controls consisting of all other cancer sites excluding lung cancer and cancers of unknown primary site. Lifetime occupational history was obtained through a self-administered questionnaire and used in conjunction with a job exposure matrix to estimate the participants' lifetime cumulative exposure to approximately 180 active compounds in pesticides. Conditional logistic regression was used to assess prostate cancer risk, adjusting for potential confounding variables and effect modifiers. These include age, ethnicity, alcohol consumption, smoking, education, and proxy respondent. RESULTS AND CONCLUSIONS: The significant association between prostate cancer risk and exposure to DDT (OR = 1.68; 95% CI: 1.04-2.70 for high exposure), simazine (OR = 1.89; 95% CI: 1.08-3.33 for high exposure), and lindane (OR = 2.02; 95% CI: 1.15-3.55 for high exposure) is in keeping with those previously reported in the literature. We also observed a significant excess risk for several active ingredients that have not been previously reported in the literature such as dichlone, dinoseb amine, malathion, endosulfan, 2,4-D, 2,4-DB, and carbaryl. Some findings in our study were not consistent with those reported in the literature, including captan, dicamba, and diazinon. It is possible that these findings showed a real association and the inconsistencies reflected differences of characteristics between study populations.

Exposure to anesthetic gases and congenital anomalies in offspring of female registered nurses.

BACKGROUND: Studies of offspring of mothers exposed to anesthetic gases have shown associations with congenital anomalies reported by the mothers, but rarely in studies with objectively ascertained outcomes. We conducted a retrospective cohort study to examine associations between registry-ascertained congenital anomalies in offspring and anesthetic gas exposure of mothers employed as nurses. METHODS: A cohort of registered nurses in British Columbia, Canada, was linked to records of births and congenital anomalies from 1990 to 2000. Exposures were assessed via a survey of anesthetic gas use in all hospitals in the province and records of nurses' jobs, departments, and hospitals. RESULTS: Departments most frequently reporting anesthetic gas use were operating rooms, post-anesthetic recovery rooms, and maternity units. In the cohort of 15,317 live-borne children of 9,433 mothers, 1,079 had congenital anomalies. Anomalies were associated with ever and probable maternal exposure to halogenated gases (ORs: 1.49, 95% CI: 1.04-2.13; and 2.61, 95% CI: 1.31-5.18, respectively) and to nitrous oxide (ORs: 1.42, 95% CI: 1.05-1.94; and 1.82, 95% CI: 1.11-2.99). Anomalies most frequently associated with exposure were those of the heart (OR, halogenated gases: 2.31, 95% CI: 1.07-4.97) and integument (OR, halogenated gases: 3.56, 95% CI: 1.53-8.32; OR, nitrous oxide: 3.02, 95% CI: 1.37-6.64). Gases most frequently associated with anomalies were halothane (predominantly used early in the study period), isoflurane, and sevoflurane (predominantly used later in the period). CONCLUSIONS: In this study, where both exposures and outcomes were assessed objectively, certain congenital anomalies were associated with estimated anesthetic gas exposure.

Rates of congenital anomalies and other adverse birth outcomes in an offspring cohort of registered nurses from British Columbia, Canada.

OBJECTIVES: Although there is concern that occupational exposures in some nursing professions may confer reproductive risks, there are few relevant studies. Our objective is to determine if a cohort of female registered nurses (RN) from British Columbia (BC), in comparison to BC women in general, have elevated rates of congenital anomalies, stillbirths, low birth weight, or prematurity in their offspring. METHODS: A cohort of RNs from BC was linked to Vital Statistics birth records and the BC Health Status Registry (HSR) between the years 1986 and 2000. The RN offspring cohort included 23,222 births. For each outcome, odds ratios (OR) with 95% confidence intervals (CI) were determined by comparing rates in the nurses' cohort with the rates in the general population standardized for the year of birth. RESULTS: Apart from chromosomal anomalies, for each of the ICD-9 congenital anomaly categories there were fewer congenital anomalies than expected, resulting in an overall prevalence of congenital anomaly cases (with at least one anomaly) that was significantly lower in the RN cohort (1,567 observed vs. 1,846 expected; OR 0.84, 95% CI 0.78-0.90) in comparison to the general population. Low birth weight (1,138 observed vs. 1,260 expected; OR 0.90, 95% CI 0.83-0.98) was also significantly lower, while prevalence of prematurity and stillbirths were not significantly different than among the general population. CONCLUSION: Offspring of RNs in BC had a lower prevalence of congenital anomalies and low birth weight compared to the rates found among the general population. Further studies are underway to determine if subpopulations within the RN cohort are at risk.

Identifying related cancer types based on their incidence among people with multiple cancers.

BACKGROUND: There are several reasons that someone might be diagnosed with more than one primary cancer. The aim of this analysis was to determine combinations of cancer types that occur more often than expected. The expected values in previous analyses are based on age-and-gender-adjusted risks in the population. However, if cancer in people with multiple primaries is somehow different than cancer in people with a single primary, then the expected numbers should not be based on all diagnoses in the population. METHODS: In people with two or more cancer types, the probability that a specific type is diagnosed was determined as the number of diagnoses for that cancer type divided by the total number of cancer diagnoses. If two types of cancer occur independently of one another, then the probability that someone will develop both cancers by chance is the product of the individual probabilities for each type. The expected number of people with both cancers is the number of people at risk multiplied by the separate probabilities for each cancer. We performed the analysis on records of cancer diagnoses in British Columbia, Canada between 1970 and 2004. RESULTS: There were 28,159 people with records of multiple primary cancers between 1970 and 2004, including 1,492 people with between three and seven diagnoses. Among both men and women, the combinations of esophageal cancer with melanoma, and kidney cancer with oral cancer, are observed more than twice as often as expected. CONCLUSION: Our analysis suggests there are several pairs of primary cancers that might be related by a shared etiological factor. We think that our method is more appropriate than others when multiple diagnoses of primary cancer are unlikely to be the result of therapeutic or diagnostic procedures.

Methodology to identify Iranian immigrants for epidemiological studies.

Determining ethnic differences in cancer patterns using administrative databases is often a methodological challenge for information on ethnicity or place of birth is commonly lacking. This paper describes the approach we used to identify Iranians residing in British Columbia (BC), Canada and who were registered within the BC Cancer Registry. A listing of common Iranian surnames and given names was generated from two sources: a residential telephone book (with a high density of Iranians) and a provincial breast cancer screening program (which allowed for the selection of women born in Iran). Surnames and given names were reviewed manually and the Iranian names were identified and coded as 'highly probable' and 'probable' Iranian. A name directory was then created and linked with the BC Cancer Registry to identify Iranian cancer cases. Using this method, 1729 surnames and 737 given names were selected from the telephone book, and 1881 surnames and 757 given names from the screening program. The majority of these names were coded as 'highly probable' Iranian (98% and 96% for surnames and given names, respectively). 12% of surnames and 10% of given names were common to both sources. A listing of the most common Iranian surnames and given names is provided. In conclusion, in the absence of other ethnicity data, surnames and given names can be very helpful to identify persons of specific ethnicities when these ethnic groups have distinctive names.

Demographic and tumor characteristics of patients diagnosed with nonmelanoma skin cancer: 13-year retrospective study.

BACKGROUND: The incidence of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) is increasing worldwide; however, this varies by region. To date, there are limited data about trends of nonmelanoma skin cancer (NMSC) in Canada. OBJECTIVE: To determine the demographic and tumor characteristic changes in patients diagnosed with BCC and SCC from 1993 to 2005 in a dermatology practice in Vancouver, British Columbia. METHOD: A retrospective chart review was conducted on patients with biopsy-confirmed NMSC between 1993 and 2005. Demographic and tumor characteristics were documented for the first two incident BCCs and SCCs per patient, and a descriptive data analysis was undertaken. RESULTS: A total of 1,177 NMSCs were identified from 885 patient charts. The number of BCCs increased from 1993 to 2003 and then decreased until 2005. BCCs and SCCs were generally diagnosed in older people (60+ years); however, an important group of younger patients (20-39 years) was also diagnosed with BCCs. BCCs and SCCs were most commonly seen on the head and neck, but the leg was a common location for SCC in women. CONCLUSION: NMSC is prevalent in British Columbia. These results highlight the fact that NMSC can affect individuals younger than 40 years old. Prevention strategies are warranted to reduce the burden of NMSC in British Columbia.

Breast cancer incidence and neighbourhood income.

BACKGROUND: In developed countries, women of higher socioeconomic status often have higher breast cancer incidence rates, compared with women of lower socioeconomic status. DATA AND METHODS: Data were extracted from the Canadian Cancer Registry for the 229,955 cases of adult female invasive breast cancer diagnosed from 1992 through 2004. Postal code at diagnosis was used to determine neighbourhood income quintile. Breast cancer incidence was examined by year, region, age and neighbourhood income quintile. Census data for 1991 on children ever born and British Columbia data for 2006 on first-time attendance at mammography screening were analyzed by neighbourhood income quintile. RESULTS: Residence in the lowest as opposed to the highest neighbourhood income quintile was associated with a 15% lower risk of being diagnosed with breast cancer. Higher income levels were associated with lower parity in 1991 and a higher prevalence of first-time screening mammography in British Columbia in 2006. INTERPRETATION: Canadian data support an association between the diagnosis of invasive breast cancer and neighbourhood income quintile. Parity and mammography screening may account for some differences in incidence.

Hospitalisations 1998-2000 in a British Columbia population-based cohort of young cancer survivors: report of the Childhood/Adolescent/Young Adult Cancer Survivors (CAYACS) Research Program.

BACKGROUND AND OBJECTIVES: Because of late effects among survivors of cancer in young people, increased hospitalisations would be expected. This study determined the occurrence, frequency and days in hospital (DIH) of hospital admissions among 5-year survivors of childhood and adolescent cancer diagnosed in British Columbia (BC), compared hospitalisation risk with the general population and examined the impact of sociodemographic, health care system and clinical factors. DESIGN: This population-based study frequency matched 1157 survivors of cancer diagnosed before 20 years of age from 1970 to 1992 from the BC Cancer Registry with 11,570 randomly selected individuals from BC's health insurance plan Client Registry. Administrative hospitalisation records from 1998 to 2000 were linked to study cohorts, and regression and trend analyses were carried out. RESULTS: From 1998 to 2000, 240 (21%) of survivors and 614 (5.3%) of the population sample were admitted to hospital at least once [adjusted OR=4.36 (95% CI 3.68-5.16)]. Hospitalised survivors had a higher average number of admissions (2.0 versus 1.5 admissions, respectively) and longer mean DIH (10.9 versus 7.8d, respectively) than hospitalised population controls. Female gender and older age increased the risk of hospitalisation, as did the presence of a relapse or second cancer by 5 years post-diagnosis. CONCLUSION: Our cohort of child and adolescent cancer survivors had higher odds of hospitalisation, more admissions among those hospitalised and longer stay in hospital compared to the population sample. This has implications for health care system resources and appropriate management of late effects of survivors.

Occupational female breast and reproductive cancer mortality in British Columbia, Canada, 1950-94.

BACKGROUND: It has been postulated that recent increases in female breast and reproductive cancers may be, in part, attributable to occupational exposures. AIM: We aimed to identify occupational associations with female breast and reproductive cancer mortality among women living in British Columbia (BC), Canada. METHODS: Case-control methods were used to calculate mortality odds ratios for occupation and cause of death information obtained from the provincial death registry. Cases included women 20 years of age or older who died from breast or reproductive cancer between 1950 and 1994 and resident in BC, Canada. Controls were randomly selected from non-cancer deaths, matched according to age at death and year of death. In a subsequent, stratified analysis, we also identified changes over time to breast and reproductive cancer mortality among each worker group. RESULTS: There was excess mortality from breast and ovarian cancer among teachers, nurses, secretaries, librarians, retail sales clerks and religious workers. An elevated risk of breast cancer mortality was also found among professionals employed as owners, managers and government officials, financial saleswomen, scientists, physicians, medical and dental technicians and accountants. Secretaries, telephone operators and musicians were at increased risk of death from endometrial cancer. Cervical cancer mortality was not significantly increased for any occupational classification. CONCLUSIONS: Our study was aimed primarily at hypothesis generation. More systematic reviews, including cancer registry studies, will prove useful for confirming the relationships we have observed, including a possible increase in the risk of breast and ovarian cancer mortality among women employed in professional occupations.

Mortality among 5-year survivors of cancer diagnosed during childhood or adolescence in British Columbia, Canada.

BACKGROUND: Ongoing monitoring of late mortality among survivors of a childhood or adolescent cancer is essential to appropriately evaluate risk in more recent cohorts and with longer follow-up. We examined overall and cause-specific mortality in a population-based cohort of 2,354 individuals diagnosed with a cancer or tumor prior to 20 years of age between 1970 and 1995 in British Columbia (BC), Canada who survived at least 5 years. PROCEDURE: Late deaths in a survivor cohort ascertained from the BC Cancer Registry were identified using death registrations. Standardized mortality ratios, absolute excess risk of death, and cumulative risk of death were determined. Demographic, temporal, and disease-related factors in risk of late mortality were also assessed. RESULTS: After 24,491 person-years of follow-up, there were 181 deaths, 139 of which were cancer related. Excess risk of late mortality among survivors was 7 deaths per 1,000 person-years at risk (AER = 6.6). Standardized mortality ratio (SMR) was ninefold higher relative to the underlying BC population (SMR = 9.1, 95% CI, 7.8-10.5), and was greatest for those with a recurrence within 5 years of diagnosis, and for those diagnosed with acute lymphoblastic leukemia and nervous system tumors. Absolute excess risk of late death was significantly higher for males and for those diagnosed prior to 1980, but did not vary according to age at diagnosis. Relative mortality was significantly increased due to cancer-related causes of death (SMR = 81.7, 95% CI, 68.6-95.8), as well as circulatory (SMR = 9.7, 95% CI, 4.2-19.1) and respiratory (SMR = 16.8, 95% CI, 4.6-43.0) diseases. CONCLUSIONS: In this population-based cohort with long follow-up, there continues to be excess late mortality among childhood and adolescent cancer survivors due to both cancer and non-cancer causes, even among more recently diagnosed survivors.

Socioeconomic status and childhood solid tumor and lymphoma incidence in Canada.

The authors examined the relation between neighborhood income, as a measure of socioeconomic status, and childhood cancer. Incident cases of childhood solid tumor and lymphoma in 1985-2001 were identified from provincial cancer registries in Canada. Residential postal codes at the time of diagnosis were used to assign cases to census neighborhoods. Person-years at risk were determined from quintiles of population by neighborhood income, sex, and 5-year age group, constructed using census population data. Poisson regression was used to calculate incidence rate ratios across neighborhood income quintiles. Compared with the incidence rate in the richest income quintile, moderately lower rate ratios of 0.73 (95% confidence interval: 0.63, 0.86) and 0.84 (95% confidence interval: 0.69, 1.04) were observed, respectively, for carcinomas and renal tumors in the poorest income quintile. No association was found for other types of cancer. Although a potential relation between socioeconomic status and childhood cancer cannot be excluded, the overall pattern seems compatible with random variation.

Physical and emotional health effects and social consequences after participation in a low-fat, high-carbohydrate dietary trial for more than 5 years.

PURPOSE: Little is known about the potential adverse effects of interventions to reduce dietary fat. We examined the physical and emotional health effects, and social consequences experienced by women at high risk for breast cancer who had participated in a low-fat diet intervention, randomized, controlled trial for at least 5 years. METHODS: Participants in the Canadian Diet and Breast Cancer Prevention Trial from British Columbia were mailed a survey questionnaire that included the validated Medical Outcomes Study 36-item Short Form Health Survey (SF-36) and Women's Health Questionnaire (WHQ), and a series of questions on health-related and social constructs. Responses were compared between the diet intervention and control groups by menopausal status. RESULTS: Completed questionnaires were returned by 359 women in the diet intervention group and 382 in the control group. No significant differences were found between these groups for SF-36 and WHQ health outcomes, hair/nail changes, physical activity levels, family/friend support levels, and doctor visits. Significantly more women in the intervention group reported taking products for arthritis (other than pain medication), greater difficulty in maintaining eating habits in social situations and at work, greater stress, and guilt related to personal eating habits. These findings persisted for both premenopausal and postmenopausal women. CONCLUSION: Changes resulting from a low-fat diet intervention can be incorporated into women's daily lives with limited long-term negative effects.

Childhood leukemia and socioeconomic status in Canada.

BACKGROUND: Leukemia is one of the most common potentially fatal illnesses in children, and its causes are not well understood. Although socioeconomic status (SES) has been related to leukemia in some studies, this apparent association may be attributable to ascertainment or participation bias. This study was undertaken to determine whether there is a difference in incidence of childhood leukemia for different levels of SES, as measured by neighborhood income, in an unselected population case group. METHODS: All cases of childhood leukemia diagnosed in the years 1985-2001 were identified from population-based cancer registries in Canada. Postal codes for the place of residence at diagnosis were used to ascertain the census neighborhoods for cases. We constructed neighborhood-based income quintiles from census population data, and stratified the population at risk by sex and 5-year age groupings. Age-standardized incidence rates and 95% confidence intervals (CIs) were calculated. We used Poisson regression to compare incidence rate ratios (RRs) across income quintiles. RESULTS: A slightly lower relative risk of childhood leukemia was observed in the poorest quintile compared with the richest (RR = 0.87; 95% CI = 0.80-0.95). The lower risk in the poorest quintile was restricted to acute lymphoid leukemia (0.86; 0.78-0.95) and was strengthened slightly by restriction to urban areas (0.83; 0.74-0.93). CONCLUSIONS: This analysis suggests that high SES is a true risk factor for childhood leukemia and that inconsistent results from other studies may be related to differences in case ascertainment or study participation.