Periodic trends in geographical variation of prostate cancer incidence and mortality in Finland between 1985 and 2019

Background: Evaluation of regional variation of prostate cancer (PCa) incidence and PCa-specific mortality is essential in the assessment of equity in a national healthcare system. We evaluated PCa incidence and PCa-specific mortality between different municipalities and hospital districts in Finland over 1985–2019. Material and Methods: Men diagnosed with PCa in Finland from 1985 through 2019 were retrieved from Finnish Cancer Registry. Age-standardized PCa incidence and mortality rates were estimated by municipality and hospital district as well as municipality urbanization, education, and income level using hierarchical Bayesian modeling. Standard deviations (SD) of the regional rates were compared between periods from 1985–1989 to 2015–2019. Results: We identified 123,185 men diagnosed with any stage PCa between 1985 and 2019. SD of PCa incidence rate (per 100,000 person-years) showed that the total variation of PCa incidence between different municipalities was substantial and varied over time: from 22.2 (95% CI, 17.1–27.8) in 1985–1989 to 56.5 (95% CI, 49.8–64.5) in 2000–2004. The SD of PCa mortality rate between all municipalities was from 9.0 (95% CI, 6.6–11.8) in 2005–2009 to 2.4 (95% CI, 0.9–4.8) in 2015–2019. There was a trend toward a lower PCa-specific mortality rate in municipalities with higher education level. Discussion: Regional variation in the incidence rate of PCa became more evident after initiation of PSA testing in Finland, which indicates that early diagnostic practice (PSA testing) of PCa has been different in different parts of the country. Variation in the national PCa mortality rate was indeed recognizable, however, this variation diminished at the same time as the mortality rate declined in Finland. It seems that after the initiation period of PSA testing, PSA has equalized PCa mortality outcomes in Finland.