Christine M. Friedenreich

Cancer incidence attributable to insufficient fruit and vegetable consumption in Alberta in 2012

BACKGROUND Sufficient fruit and vegetable consumption (≥ 5 servings/d) has been associated with a probable decreased risk for cancers of the oral cavity, pharynx, larynx, esophagus, stomach and lung (fruit only). The purpose of this study was to estimate the proportion and absolute number of cancer cases in Alberta in 2012 that were attributable to insufficient fruit and vegetable consumption. METHODS The numbers and proportions of cancers attributable to insufficient fruit and vegetable consumption were estimated using the population attributable risk. Relative risks were obtained from international collaborative panels and peer-reviewed literature. Prevalence data for insufficient fruit and vegetable consumption in Alberta were obtained from the Canadian Community Health Survey (2003, 2004, 2005, 2007/08). Age-, site- and sex-specific cancer incidence data for 2012 were obtained from the Alberta Cancer Registry. RESULTS The proportion of men consuming 5 or more servings of fruits and vegetables per day ranged from 25.9%-30.4% across age groups; the range among women was 46.8%-51.5% across age groups. The proportion of cancers attributable to insufficient fruit and vegetable consumption in Alberta was highest for esophageal cancer (40.0%) and lowest for lung cancer (3.3%). Overall, 290 cancer cases (1.8%) in Alberta in 2012 were attributable to insufficient fruit and vegetable consumption. INTERPRETATION Almost 2% of cancers in Alberta can be attributed to insufficient fruit and vegetable consumption. A diet rich in fruits and vegetables has benefits for the prevention of cancer and other chronic diseases; thus, increasing the proportion of Albertans who meet cancer prevention guidelines for fruit and vegetable consumption is a priority.

Cancer incidence attributable to red and processed meat consumption in Alberta in 2012

BACKGROUND Consumption of red and processed meats has been associated with an increased risk of colorectal cancer. The purpose of this study was to estimate the proportion and absolute number of cancers in Alberta in 2012 that could be attributed to the consumption of red and processed meat. METHODS The number and proportion of colorectal cancers in Alberta that were attributable to red and processed meat consumption were estimated using population attributable risk. Relative risks were obtained from the World Cancer Research Funds 2011 Continuous Update Project on Colorectal Cancer, and the prevalence of red and processed meat consumption was estimated using dietary data from Albertas Tomorrow Project. Age- and sex-specific colorectal cancer incidence data for 2012 were obtained from the Alberta Cancer Registry. RESULTS Among participants in Albertas Tomorrow Project, 41%-61% of men and 14%-25% of women consumed more than 500 g of red and processed meat per week, which exceeds World Cancer Research Fund cancer prevention guidelines. For red meat consumption, population attributable risks for colorectal cancer were substantially higher for men (13.6%-17.9%) than for women (1.6%-2.1%). For processed meat consumption, the population attributable risks were also higher for men (3.2%-4.8%) than for women (1.5%-2.1%). Overall, about 12% of colorectal cancers, or 1.5% of all cancers, in Alberta in 2012 were attributable to the consumption of red and processed meat. INTERPRETATION Red and processed meat consumption is estimated to acount for about 12% of colorectal cancers in Alberta. Decreasing its consumption has the potential to reduce to Albertas cancer burden.

Cancer incidence attributable to inadequate physical activity in Alberta in 2012

BACKGROUND Physical inactivity has been consistently associated with increased risk of colorectal, endometrial, breast (in postmenopausal women), prostate, lung and ovarian cancers. The objective of the current analysis was to estimate the proportion and absolute number of site-specific cancer cases attributable to inadequate physical activity in Alberta in 2012. METHODS We used population attributable risks to estimate the proportion of each site-specific cancer attributable to inactivity. Relative risk estimates were obtained from the epidemiological literature, and prevalence estimates were calculated with the use of data from the Canadian Community Health Survey cycle 2.1 (2003). Respondents who acquired 1.5-2.9 kcal/kg per day and less than 1.5 kcal/kg per day of physical activity were classified as moderately active and inactive, respectively, and both levels were considered inadequate for mitigating cancer risks. We obtained age-, sex- and site-specific cancer incidence data from the Alberta Cancer Registry for 2012. RESULTS About 59%-75% of men and 69%-78% of women did not engage in adequate physical activity. Overall, 13.8% of cancers across all associated cancers were estimated to be attributable to inadequate physical activity, representing 7.2% of all cancers diagnosed in Alberta in 2012. Suboptimal levels of physical activity had a greater impact among women: the proportion of all associated cancers attributable to inadequate physical activity was 18.3% for women and 9.9% for men. INTERPRETATION A substantial proportion of cancer cases diagnosed in Alberta were estimated to be attributable to inadequate physical activity. With the high prevalence of physical inactivity among adults in the province, developing strategies to increase physical activity levels could have a notable impact on reducing future cancer burden in Alberta.

Cancer incidence attributable to excess body weight in Alberta in 2012

BACKGROUND Excess body weight has been consistently associated with colorectal, breast, endometrial, esophageal, gall bladder, pancreatic and kidney cancers. The objective of this analysis was to estimate the proportion of total and site-specific cancers attributable to excess body weight in adults in Alberta in 2012. METHODS We estimated the proportions of attributable cancers using population attributable risk. Risk estimates were obtained from recent meta-analyses, and exposure prevalence estimates were obtained from the Canadian Community Health Survey. People with a body mass index of 25.00-29.99 kg/m2 and of 30 kg/m2 or more were categorized as overweight and obese, respectively. RESULTS About 14%-47% of men and 9%-35% of women in Alberta were classified as either overweight or obese; the proportion increased with increasing age for both sexes. We estimate that roughly 17% and 12% of obesity-related cancers among men and women, respectively, could be attributed to excess body weight in Alberta in 2012. The heaviest absolute burden in terms of number of cases was seen for breast cancer among women and for colorectal cancer among men. Overall, about 5% of all cancers in adults in Alberta in 2012 were estimated to be attributable to excess body weight in 2000-2003. INTERPRETATION Excess body weight contributes to a substantial proportion of cases of cancers associated with overweight and obesity annually in Alberta. Strategies to improve energy imbalance and reduce the proportion of obese and overweight Albertans may have a notable impact on cancer incidence in the future.

Cancer incidence attributable to lifestyle and environmental factors in Alberta in 2012: summary of results

BACKGROUND Estimates of the proportion of cancer cases that can be attributed to modifiable risk factors are not available for Canada and, more specifically, Alberta. The purpose of this study was to estimate the total proportion of cancer cases in Alberta in 2012 that could be attributed to a set of 24 modifiable lifestyle and environmental risk factors. METHODS We estimated summary population attributable risk estimates for 24 risk factors (smoking [both passive and active], overweight and obesity, inadequate physical activity, diet [inadequate fruit and vegetable consumption, inadequate fibre intake, excess red and processed meat consumption, salt consumption, inadequate calcium and vitamin D intake], alcohol, hormones [oral contraceptives and hormone therapy], infections [Epstein-Barr virus, hepatitis B and C viruses, human papillomavirus, Helicobacter pylori], air pollution, natural and artificial ultraviolet radiation, radon and water disinfection by-products) by combining population attributable risk estimates for each of the 24 factors that had been previously estimated. To account for the possibility that individual cancer cases were the result of a combination of multiple risk factors, we subtracted the population attributable risk for the first factor from 100% and then applied the population attributable risk for the second factor to the remaining proportion that was not attributable to the first factor. We repeated this process in sequential order for all relevant exposures. RESULTS Overall, an estimated 40.8% of cancer cases in Alberta in 2012 were attributable to modifiable lifestyle and environmental risk factors. The largest proportion of cancers were estimated to be attributable to tobacco smoking, physical inactivity and excess body weight. The summary population attributable risk estimate was slightly higher among women (42.4%) than among men (38.7%). INTERPRETATION About 41% of cancer cases in Alberta may be attributable to known modifiable lifestyle and environmental risk factors. Reducing the prevalence of these factors in the Alberta population has the potential to substantially reduce the provincial cancer burden.

Breastfeeding and Endometrial Cancer Risk: An Analysis From the Epidemiology of Endometrial Cancer Consortium.

OBJECTIVE To investigate the association between breastfeeding and endometrial cancer risk using pooled data from 17 studies participating in the Epidemiology of Endometrial Cancer Consortium. METHODS We conducted a meta-analysis with individual-level data from three cohort and 14 case-control studies. Study-specific odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for the association between breastfeeding and risk of endometrial cancer using multivariable logistic regression and pooled using random-effects meta-analysis. We investigated between-study heterogeneity with I  and Q statistics and metaregression. RESULTS After excluding nulliparous women, the analyses included 8,981 women with endometrial cancer and 17,241 women in a control group. Ever breastfeeding was associated with an 11% reduction in risk of endometrial cancer (pooled OR 0.89, 95% CI 0.81-0.98). Longer average duration of breastfeeding per child was associated with lower risk of endometrial cancer, although there appeared to be some leveling of this effect beyond 6-9 months. The association with ever breastfeeding was not explained by greater parity and did not vary notably by body mass index or histologic subtype (grouped as endometrioid and mucinous compared with serous and clear cell). CONCLUSION Our findings suggest that reducing endometrial cancer risk can be added to the list of maternal benefits associated with breastfeeding. Ongoing promotion, support, and facilitation of this safe and beneficial behavior might therefore contribute to the prevention of this increasingly common cancer.

Lung cancer incidence attributable to residential radon exposure in Alberta in 2012

BACKGROUND Radon is carcinogenic, and exposure to radon has been shown to increase the risk of lung cancer. The objective of this study was to quantify the proportion and number of lung cancer cases in Alberta in 2012 that could be attributed to residential radon exposure. METHODS We estimated the population attributable risk of lung cancer for residential radon using radon exposure data from the Cross-Canada Survey of Radon Concentrations in Homes from 2009-2011 and data on all-cause and lung cancer mortality from Statistics Canada from 2008-2012. We used cancer incidence data from the Alberta Cancer Registry for 2012 to estimate the total number of lung cancers attributable to residential radon exposure. Estimates were also stratified by sex and smoking status. RESULTS The mean geometric residential radon level in Alberta in 2011 was 71.0 Bq/m3 (geometric standard deviation 2.14). Overall, an estimated 16.6% (95% confidence interval 9.4%-29.8%) of lung cancers were attributable to radon exposure, corresponding to 324 excess attributable cancer cases. The estimated population attributable risk of lung cancer due to radon exposure was higher among those who had never smoked (24.8%) than among ever smokers (15.6%). However, since only about 10% of cases of lung cancer occur in nonsmokers, the estimated total number of excess cases was higher for ever smokers (274) than for never smokers (48). INTERPRETATION With about 17% of lung cancer cases in Alberta in 2012 attributable to residential radon exposure, exposure reduction has the potential to substantially reduce Albertas lung cancer burden. As such, home radon testing and remediation techniques represent important cancer prevention strategies.

Cancer incidence attributable to the use of oral contraceptives and hormone therapy in Alberta in 2012

BACKGROUND Hormonal contraceptives and hormone replacement therapies are classified as carcinogenic to humans (group 1) by the International Agency for Research on Cancer. We sought to estimate the proportion and total number of cancers attributable to the use of oral contraceptives and hormone therapy in Alberta in 2012. METHODS Population attributable risks were used to estimate the proportion of attributable cases for each associated cancer site. Relative risk estimates were obtained from the most relevant and recent epidemiologic literature. Prevalences of the use of oral contraceptives and hormone therapy in Alberta were collected from Albertas Tomorrow Project. Specific cancer incidence data were obtained from the Alberta Cancer Registry for the year 2012. RESULTS Overall, 6.3% of breast cancers (n = 135) diagnosed in Alberta in 2012 were estimated to be attributable to the use of oral contraceptives, and the exposure potentially prevented about 57.3% of endometrial cancers (n = 276) and 29.1% of ovarian cancers (n = 52). About 15.5% of breast cancers (n = 258) and 8.9% of ovarian cancers (n = 13) were estimated to be attributable to the use of hormone therapy, whereas 11.3% of endometrial cancers (n = 48) were possibly prevented by the exposure. INTERPRETATION Based on our estimates, oral contraceptive use resulted in a net protective effect among the cancer sites studied, thus reducing the cancer burden in Alberta in 2012. The use of hormone therapy was estimated to increase the cancer burden in the province, therefore the risk and benefit of hormone therapy should be carefully considered before use.

Cancer incidence attributable to insufficient fibre consumption in Alberta in 2012

BACKGROUND Insufficient fibre consumption has been associated with a increased risk of colorectal cancer. The purpose of this study was to estimate the proportion and absolute number of cancers in Alberta that could be attributed to insufficient fibre consumption in 2012. METHODS The number and proportion of colorectal cancers in Alberta attributable to insufficient fibre consumption were estimated using the population attributable risk. Relative risks were obtained from the World Cancer Research Funds 2011 Continuous Update Project on colorectal cancer, and the prevalence of insufficient fibre consumption (< 23 g/d) was estimated using dietary data from Albertas Tomorrow Project. Age- and sex-specific colorectal cancer incidence data for 2012 were obtained from the Alberta Cancer Registry. RESULTS Between 66% and 67% of men and between 73% and 78% of women reported a diet with insufficient fibre consumption. Population attributable risk estimates for colorectal cancer were marginally higher in men, ranging from 6.3% to 6.8% across age groups, whereas in women they ranged from 5.0% to 5.5%. Overall, 6.0% of colorectal cancers or 0.7% of all cancers in Alberta in 2012 were estimated to be attributable to insufficient fibre consumption. INTERPRETATION Insufficient fibre consumption accounted for 6.0% of colorectal cancers in Alberta in 2012. Increasing fibre consumption in Alberta has the potential to reduce to the future burden of colorectal cancer in the province.

Cancer incidence attributable to alcohol consumption in Alberta in 2012

BACKGROUND Alcohol consumption has been associated with risk of oral cavity/pharyngeal, laryngeal, esophageal, liver, colorectal and breast cancers. The purpose of this study was to estimate the proportion and total number of these cancers in Alberta in 2012 attributable to alcohol consumption. METHODS We estimated cancers attributable to alcohol consumption in adults in Alberta using population attributable risk calculations. Relative risks were obtained from recent meta-analyses, and alcohol consumption in Alberta was quantified with the use of data from the Canadian Community Health Survey. We obtained age-, site- and sex-specific cancer incidence data for 2012 from the Alberta Cancer Registry. The impact of potential underestimation of alcohol consumption in Canadian Community Health Survey data was evaluated with the use of per-capita alcohol sales data from Statistics Canada. RESULTS Proportions of cancers attributable to alcohol consumption at individual cancer sites were estimated to be as low as 5.1% (liver) and as high as 19.9% (oral cavity/pharynx) among men and as low as 2.1% (liver) and as high as 7.6% (oral cavity/pharynx) among women in Alberta. The total number of alcohol-attributable cancer cases was highest for common cancers (colorectal, female breast), whereas at individual cancer sites, population attributable risks were highest for upper aerodigestive tract cancers. A total of 4.8% of alcohol-associated cancers (1.6% of all cancers) in Alberta could be attributed to alcohol consumption. After adjustment for recorded alcohol consumption, our estimates of population attributable risk increased to 10.7% of alcohol-associated cancers and 3.5% of all cancers. INTERPRETATION Alcohol consumption is estimated to account for 1.6%-3.5% of total cancer cases in Alberta. Given that no level of alcohol consumption is considered safe with respect to cancer risk, strategies to reduce alcohol consumption have the potential to reduce Albertas cancer burden.