International patterns and trends in testicular cancer incidence, overall and by histologic subtype, 1973-2007

Abstract

Incidence rates of testicular cancer in Northern European and North American countries have been widely reported, whereas rates in other populations, such as Eastern Europe, Central/South America, Asia, and Africa, have been less frequently evaluated. We examined testicular cancer incidence rates overall and by histologic type by calendar time and birth cohort for selected global populations 1973-2007. Age-standardized incidence rates over succeeding 5-year periods were calculated from volumes 4-9 of Cancer Incidence in Five Continents electronic database (CI5plus) and the newly released CI5X (volume 10) database. Annual percent change over the 35-year period was calculated using weighted least squares regression. Age-period-cohort analyses were performed and observed rates and fitted rate ratios presented by birth cohort. Incidence rates of testicular cancer increased between 1973-1977 and 2003-2007 in most populations evaluated worldwide. Of note, incidence rates in Eastern European countries rose rapidly and approached rates in Northern European countries. Rates in Central and South America also increased and are now intermediate to the high rates among men of European ancestry and low rates among men of Asian or African descent. Some heterogeneity in the trends in seminoma and nonseminoma were observed in Denmark, the United Kingdom, and among US whites, particularly in recent generations, with rapid and uniform increases in the incidence of both histologic types in Slovakia. Reasons for the rising incidence rates among European and American populations remain unexplained; however, changing distributions in the prevalence of risk factors for testicular cancer cannot be ruled out.

Keywords: birth cohort; international trends; seminoma; testicular cancer incidence.

Figure 1

Annual Percent Change (APC) in age-adjusted incidence rate from 1973-1977 through 2003-2007 plotted by the age-adjusted rate in 2003-2007. Triangles represent populations in which the APC increased (p-value < 0.05), circles represent populations in which the APC remained constant (p-value ≥ 0.05), and the diamond represents the population in which the APC decreased across the time period evaluated (p-value < 0.05).

Figure 2

Trends in age-adjusted testicular cancer rates by continent and registry/country (1973-1977 through 2003-2007). Rates are per 100,000 man-years and adjusted to the World Standard population.

Figure 3

Incidence rates of testicular cancer by histologic type (per 100,000 man-years) age-adjusted to the world standard population for selected populations during 2003-2007.

Figure 4

Trends in age-adjusted testicular cancer rates by calendar period for seminoma and nonseminoma, 1973-2007. Rates are per 100,000 man-years, adjusted to the world standard population.

Figure 5

Testicular cancer incidence rates per 100,000 man-years by year of birth for seminoma (top) and nonseminoma (bottom) from four selected countries. Rates are displayed on a semilog scale. For each graph, rates in the 5-year age-groups 15-19, 20-24, …, 50-54 years are plotted.

Figure 6

Histology-specific testicular cancer incidence: longitudinal rates per 100,000 man-years (left) and incidence rate ratios by birth cohort (right) in four selected countries. Rates are adjusted to the world standard population. Incidence rate ratios are relative to the reference cohort, midpoint 1955.