Purpose: The incidence rate of testicular germ cell cancer in Denmark increased up to the 1990s to become among the highest in the world. Since recently rate stabilization was suggested, we determined whether it is due to an increasing number of immigrants at lower risk for this cancer.
Materials and methods: The immigration status of more than 3.6 million men registered in the Danish Central Population Register between 1978 and 2003 was defined by birthplace (first generation immigrant) or parental birthplace (second generation immigrant). Linkage with the Danish Cancer Registry yielded 6,478 testicular cancer cases. Differences between populations are shown as SIR with the 95% CI.
Results: The testicular germ cell cancer incidence rate in first generation immigrants was lower than in native born Danish men (SIR 0.4, 95% CI 0.4-0.5). The rate in second generation immigrants was similar (SIR 0.9, 95% CI 0.7-1.1). The impact of immigrant status on the incidence rate increased with time from 0.6% in 1978 to 8.2% in 2003. Recent incidence rates in all men and only in men born in Denmark suggest stabilization.
Conclusions: Our finding of a higher incidence rate in second generation immigrants than in their immigrant fathers confirms the early life programming of environmental factors in the etiology of testicular cancer. Our study also shows that trend analysis of the incidence rate of this cancer should consider immigration due to considerable country specific differences in morbidity.
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