Geospatial and temporal variation of prostate cancer incidence.

ABSTRACT

OBJECTIVES: The objective of this study was to evaluate geographical and temporal variations in prostate cancer incidence in Victoria, Australia. STUDY DESIGN & METHODS: This study analysed 105,349 cases of incident prostate cancer between 1982 and 2016 from the population-based Victorian Cancer Registry. We performed Poisson regression analyses to identify an association between an annual number of prostate cancer counts, prostate-specific antigen (PSA) tests and the elderly male population (≥65) after adjusting for population at risk and years. We also applied Bayesian spatial-temporal models to determine any association with prostate cancer incidence and area-level factors. RESULTS: The overall trend of the age-standardized prostate cancer incidence was increasing. The highest age-specific incidence was observed among people aged 65-74 years in the pre- and post-PSA periods. Every increase in 1000 PSA tests per 100,000 population, prostate cancer incidence increased by 17% (relative risk [RR] = 1.17, 95% confidence interval [CI] = 1.13-1.22). A 1% increase in the proportion of the male population (≥65) correlated with a 7% increase in prostate cancer cases (RR = 1.07, 95% CI = 1.06-1.10). Compared with early PSA periods, decreasing trends of low-grade cases and growing trends of high- and intermediate-grade cases were observed after a decline in PSA test usage in late PSA periods. Men living in the most socioeconomically advantaged postal areas had a decreased risk of prostate cancer (RR = 0.914, 95% CI = 0.858-0.976). CONCLUSIONS: Age-specific risk of developing biological prostate cancer, temporal changes in PSA testing and an increasingly elderly population contributed to an increasing trend of prostate cancer incidence. When incidence trends were investigated at a more granular geographic level, socioeconomically advantaged status was associated with decreased prostate cancer risk.