Germ-cell testicular cancer in offspring of Finnish immigrants to Sweden.

Variation in testicular cancer incidence can be used to assist in identification of risks. Finland has a significantly lower germ-cell testicular cancer risk than Sweden. Finns who immigrate to Sweden maintain their lower risk irrespective of age at immigration. We investigated difference in risk between Finland and Sweden by examining germ-cell testicular cancer incidence in males born in Sweden to Finnish immigrant parents. Swedish general population registers were used to identify 11,662 males born in Sweden where both Finnish parents immigrated to Sweden from Finland from 1969 or afterward. All of these offspring were at least 15 years old by final follow-up in 2001. Some six offspring (all diagnosed between ages 20 and 24 years) had a diagnosis of germ-cell testicular cancer. Comparison with the Swedish population rate produced standardized incidence ratios [SIR (95% confidence interval)] of 0.85 (0.31-1.84) for all the men and 1.75 (0.64-3.81) for the 20- to 24-year age group. SIRs calculated using the Finnish population rates produced an overall SIR (95% confidence interval) of 1.11 (0.41-2.41) and 2.95 (1.08-6.42) for the 20- to 24-year age group. Although the substantially reduced risk of testicular cancer previously observed in Finnish immigrant to Sweden was not found, this study had insufficient statistical power to conclude that environmental exposures explain the difference in germ-cell testicular cancer risk between Finland and Sweden.