Increasing Incidence of Testicular Cancer Worldwide: A Review

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Abstract
Testicular cancer (TC) is the most common malignancy in 20 to 34-year-old men. Numerous publications have shown an increase in the incidence of testis cancer in the last 40 years with substantial differences among countries. We evaluated worldwide variations in testicular cancer incidence and compared trends in different regions in the world. We reviewed 441 studies provided by a MEDLINE search using the key words testis/testicular, cancer/tumor and incidence that were published between 1980 and 2002. From these articles we selected only those devoted to testis cancer incidence and of them only the most recent studies from each country or region. Nevertheless, articles using the same data base but providing new and additional information, for example differences among ethnic groups or controversial explanations for trends, were also retained. We selected 30 articles and analyzed their methodological approach and main results. Worldwide we observed a clear trend toward an increased TC incidence in the last 30 years in the majority of industrialized countries in North America, Europe and Oceania. Nevertheless, surprising differences in incidence rates were seen between neighboring countries (Finland 2.5/100,000 cases versus Denmark 9.2/100,000) as well as among regions of the same country (2.8 to 7.9/100,000 according to various regional French registers). In addition, substantial differences in the TC incidence and trends were observed among ethnic groups. The increase in the TC incidence was significantly associated with a birth cohort effect in the United States and in European countries. To date except for cryptorchidism no evident TC risk factor has been clearly demonstrated, although the environmental hypothesis with a key role of endocrine disrupters has been put forward by several groups. Such a recent increase in the TC rate in most industrialized countries should lead urologists and andrologists to give more attention to testicular cancer symptoms in adolescents and young adults. In a public health perspective further research using cases collected through national and regional population based registers and case-control studies must be strongly encouraged if we wish to be able to assess future trends in TC incidence rates and also identify risk factors.