Prostate-Specific Antigen Testing For Prostate Cancer: Emptying A Pool Of Susceptible Individuals?

Morten VALBERG, University of Oslo, Norway

1 Oslo Centre for Biostatistics and Epidemiology, Dept. of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
2 Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway
3 Department of Health Management and Health Economics, Institute of Health and Society, University of Oslo, Oslo, Norway
4 Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA

Purpose: After the introduction of the prostate specific antigen (PSA) test in the 1980s, a sharp increase in the incidence rate of prostate cancer was seen in the United States. The age-specific incidence patterns exhibited remarkable shifts to younger ages, and declining rates were observed at old ages. Similar trends were seen in Norway. We investigate whether these features could be explained by the existence of subgroups of the populations that are especially susceptible to prostate cancer.

Methods: We analyzed incidence data from the United States’ Surveillance, Epidemiology, and End Results program for 1973-2010, comprising 511 027 prostate cancers in men ≥40 years old, and national Norwegian incidence data for 1953-2011, comprising 113 837 prostate cancers in men ≥50 years old. We developed a statistical frailty model where only a proportion of the population can develop prostate cancer. The increased risk of being diagnosed with the cancer due to the massive use of PSA testing is taken into account.

Results: The proportion of men that were susceptible was 39.9% (95% confidence interval (CI): 38.2%, 41.6%) in the United States and 30.4% (95% CI: 28.9%, 32.0%) in Norway. The frailty model describes the changing age-specific incidence patterns across birth cohorts well.

Conclusion: The peaking cohort-specific age-incidence curves of prostate cancer may be explained by the underlying heterogeneity in prostate cancer risk. Furthermore, the introduction of the PSA test seems to have driven the peak in the incidence rate toward younger ages by inducing a larger depletion of a pool of individuals susceptible to this cancer.

Funding source: Morten Valberg was supported by the Norwegian Cancer Society, grant number 4493570.