Investigating the occupational etiology of prostate cancer in Canadian men

Prostate cancer is one of the most commonly diagnosed cancers worldwide and the etiology of prostate cancer is poorly understood. Aside from non-modifiable factors, there is limited understanding of modifiable risk factors for prostate cancer, including occupation. In epidemiological studies, job titles are generally classified into occupational or more broadly industry groupings. Previous studies have reported inconsistent findings between occupation, industry, and prostate cancer, with weak associations for farming and agriculture, rubber manufacturing, and transportation. In Canada, there have been very few large population studies that include a range of occupation and industry groups, prostate cancer outcomes, and information on non-occupational factors. The purpose of this thesis was to further investigate the occupational etiology of prostate cancer in Canadian men. By identifying occupations and industries using multiple large Canadian population based datasets, we aimed to identify consistent patterns of the multi-faceted prostate cancer – job-industry relationships. Three population based studies and one meta-analysis were conducted. Significant associations between natural resource based (agriculture, forestry, logging, wood, paper), administrative, protective services (firefighters, police, and armed forces), construction, transportation, and prostate cancer risk were observed in the three population studies. Consistent evidence for increased prostate cancer incidence and mortality among firefighting and police work was observed in the meta-analysis. Non-occupational factors including lifestyle factors and screening behaviours were also potential confounders in the relationship between occupation and prostate cancer. Overall, the results of this work provide strong evidence associating specific occupations to prostate cancer risk. Specific occupational exposures to be considered in the future are pesticides, diesel exhaust, whole body vibrations, wood dust, wood preservative chemicals, among other factors of shift work, stress, sedentary behaviour, screening patterns. These findings indicate the need for more focused studies with better exposure assessment methods and improved understanding of related non-occupational factors. Examining these factors together will inform prevention strategies for job-specific exposure and prostate cancer risk reduction. The evidence from this thesis and proposed future directions will improve knowledge on occupational risk factors related to the etiology of prostate cancer, ultimately informing policies and programs for reduction in prostate cancer risk.Ph.D