Regional trends in prostate cancer incidence, treatment with curative intent and mortality in Norway 1980–2007

Objectives: To compare the trends in prostate cancer incidence, treatment with curative intent and mortality across regions and counties in Norway, and to consider changes in incidence (an indicator for early diagnosis) and treatment with curative intent as explanatory factors for the decreasing prostate cancer mortality rates. Patients and methods: Prostate cancer incidence and mortality data (1980–2007) alongside treatment data (1987–2005) were obtained from the national, population-based Cancer Registry of Norway. Joinpoint regression models were fitted to age-adjusted incidence, treatment and mortality rates to identify linear changes in the trends. Results: Both age-adjusted incidence rates and rates of curative treatment of prostate cancer increased significantly in all five regions of Norway since the early 1990s. There was a strong positive correlation between increasing incidence and increasing use of curative treatment. The frequency of curative treatment in Western Norway was almost threefold that in the Northern and Central regions around year 2000. Subsequently, the regional trends converged and only minor differences in prostate cancer incidence and use of curative treatment were observed by 2005. The declines in mortality were observed earliest in the regions with the highest incidence and the most frequent use of curative treatment, while the largest decreases in mortality were found in counties where the largest increases in curative treatment were observed. Conclusions: The elucidation of the prostate cancer mortality trends is hindered by an inability to tease out the potential effects of early treatment from the more general impact of improved and more active treatment. However, it is likely that both sets of intervention have contributed to the decline in prostate cancer mortality in Norway since 1996.