Swedish Study Shows Lower Prostate Cancer Mortality in High-Incidence Areas
In a study reported in the Journal of the National Cancer Institute, Stattin et al found that rates of prostate cancer mortality, excess mortality in men with prostate cancer, and metastatic prostate cancer were lower in counties in Sweden with higher vs lower incidence of prostate cancer that reflected earlier vs later uptake of prostate-specific antigen (PSA) testing. The findings support the contention that more-intense opportunistic PSA testing is associated with survival benefits.
Study Details
PSA testing was introduced in Sweden in the form of opportunistic screening in 1990. A fourfold variation in proportion of men undergoing PSA testing was observed among Swedish counties, with a rapid increase in prostate cancer incidence reflecting more rapid uptake of PSA testing beginning in some counties in 1990 and not until 2000 in others. The difference in incidence between the high- and low-incidence counties was largest in 2005 and decreased thereafter, with incidence being similar in both groups of counties by 2009.
The current register- and population-based study included all men identified from the Swedish Cancer Register 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 the time periods of 1990 to 1999 and 2000 to 2009, respectively. For incidence classification, cutoffs of 100 cases per 100,000 population distinguished low-incidence and intermediate-incidence counties, and 800/100,000 distinguished intermediate- and high-incidence counties.
The incidence of metastatic prostate cancer was assessed for 2000 to 2009 and prostate cancer–specific mortality and excess mortality in men with prostate cancer were assessed for 1990 to 1999 and 2000 to 2009 by calculating rate ratios for high- vs low-incidence counties and rate ratios for the 2000 to 2009 period vs the 1990 to 1999 period within these two groups of counties.
Reduced Mortality
Overall, there were 4,528,134 person-years at risk, 1,577 deaths from prostate cancer, and 1,210 excess deaths in high-incidence counties and 2,471,373 person-years at risk, 985 prostate cancer deaths, and 878 excess deaths in low-incidence counties in the period from 2000 to 2009. In the period from 2000 to 2009, rate ratios for high- vs low-incidence counties were 0.87 (95% confidence interval [CI] = 0.81–0.95) for prostate cancer–specific mortality, 0.75 (95% CI = 0.66–0.86) for excess mortality, and 0.85 (95% CI = 0.79–0.92) for metastatic disease.
Prostate cancer–specific mortality and excess mortality were significantly lower during 2000 to 2009 than during 1990 to 1999 in high-incidence counties, with a similar but weaker trend observed in low-incidence counties. When adjusted for time periods, rate ratios for high- vs low-incidence counties were 0.81 (95% CI = 0.73–0.90) for prostate cancer–specific mortality, 0.74 (95% CI = 0.64–0.86) for excess mortality, and 0.85 (95% CI = 0.79–0.92) for metastatic prostate cancer. Rate ratios were similar in the subgroup of men aged 55 to 69 years.
Data from the National Prostate Cancer Register from 2000 to 2009 indicated that high-incidence counties had higher diagnostic and therapeutic activity, lower median age at diagnosis, a greater proportion of men with low-risk cancer, a greater proportion undergoing radical prostatectomy, and lower median PSA level at diagnosis, with differences between high- and low-incidence counties in use of radiotherapy and radical prostatectomy and PSA levels at diagnosis diminishing over time.
The investigators concluded, “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.”
Pär Stattin, MD, PhD, of Umeå University, is the corresponding author for the Journal of the National Cancer Institute article.
The study was funded by The Swedish Research Council, Swedish Cancer Society, Västerbotten County Council, and Lions Cancer Research Foundation.
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