Prostate cancer mortality in areas with high and low prostate cancer incidence

Abstract

Background: The effect of prostate-specific antigen (PSA) screening on prostate cancer mortality remains debated, despite evidence from randomized trials. We investigated the association between prostate cancer incidence, reflecting uptake of PSA testing, and prostate cancer mortality.

Methods: The study population consisted of all men aged 50 to 74 years residing in eight counties in Sweden with an early increase in prostate cancer incidence and six counties with a late increase during two time periods. Incidence of metastatic prostate cancer was investigated in the period from 2000 to 2009, and prostate cancer-specific mortality and excess mortality were investigated in the period from 1990 to 1999 and the period from 2000 to 2009 by calculating rate ratios for high- vs low-incidence counties and rate ratios for the period from 2000 to 2009 vs the period from 1990 to 1999 within these two groups. All statistical tests were two-sided.

Results: There were 4528134 person-years at risk, 1577 deaths from prostate cancer, and 1210 excess deaths in men with prostate cancer in high-incidence counties and 2471373 person-years at risk, 985 prostate cancer deaths, and 878 excess deaths in low-incidence counties in the period from 2000 to 2009. Rate ratios in counties with high vs low incidence adjusted for time period were 0.81 (95% confidence interval [CI] = 0.73 to 0.90) for prostate cancer- specific mortality and 0.74 (95% CI = 0.64 to 0.86) for excess mortality, and the rate ratio of metastatic prostate cancer was 0.85 (95% CI = 0.79 to 0.92).

Conclusions: The lower prostate cancer mortality in high-incidence counties reflecting a high PSA uptake suggests that more-intense as compared with less-intense opportunistic PSA screening reduces prostate cancer mortality.

Figure 1.

Flow chart of linkages between the Swedish Cancer Register, the Swedish Cause of Death Register, and the National Prostate Cancer Register of Sweden and final study population. * Distant metastasis defined as M1 and/or prostate-specific antigen ≥ 100ng/mL. ======= indicates registry linkage.

Figure 2.

Counties ranked by the cumulative difference between observed and predicted prostate cancer incidence per 100000 from 1995 through 2002. A) Observed and predicted age-standardized prostate cancer incidence in men aged 50–74 years in 24 Swedish counties during the period from 1980 to 2009. Steady line is predicted incidence, and undulating line is observed incidence. B) Cumulative difference between observed and predicted incidence of prostate cancer during the period from 1995 to 2009. Negative differences resulting from the predicted incidence being higher than the observed incidence in low-incidence counties were set to zero. G & B = Göteborg and Bohus county; H = high-incidence county; L = low incidence county.

Figure 3.

Prostate cancer incidence and mortality in men in Sweden aged 50 to 74 years, 2000 to 2009. A) Cumulative incidence of metastatic disease. B) Prostate cancer-specific mortality. C) Excess mortality.

Figure 4.

Risk of prostate cancer mortality according to county of residency (in groups of counties with high and low incidence) and time period in groups of counties with high, intermediate and low incidence of prostate cancer A) Rate ratio (RR) of incidence of metastatic prostate cancer, prostate cancer–specific mortality, and excess mortality in high- vs low-incidence counties. B) Rate ratio of prostate cancer–specific mortality and excess mortality in the period from 2000 to 2009 vs the period from 1990 to 1999. C) Rate ratio for high- vs low-incidence group adjusted for time period. * Metastatic prostate cancer defined as M1 and/or prostate-specific antigen ≥ 100ng/mL at diagnosis. ** Excess mortality defined as the excess number of deaths (observed minus expected), regardless of cause of death among men with prostate cancer. CI = confidence interval.