Risk of Testicular Germ Cell Cancer in Relation to Childhood Physical Activity

The only consistently reported risk factors for testicular germ-cell tumors (TGCTs) are cryptorchism, prior history of TGCT and family history of TGCT. The obesity pandemic and development of a more sedentary lifestyle have been implicated as important etiological factors in many cancers. Specifically, increased levels of physical activity have been shown to be protective against various malignancies. We examined the effect of childhood physical activity on TGCT risk. The U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) case-control study enrolled participants and their mothers between April 2002 and January 2005. Hours of sports or vigorous physical activity per week were ascertained for three time periods; 1st–5th grades, 6th–8th grades and 9th–12th grades. Son and mother-reports were analyzed separately and included 539 control son-mother pairs and 499 case son-mother pairs. Odds ratios and 95 percent confidence intervals were produced using unconditional logistic regression with adjustment for the matching variables of age, race and year of serum collection. The analysis of the sons’ responses found no relationship between childhood physical activity and TGCT whilst the mothers’ analysis found an inverse association. When the mothers’ data were stratified by histologic group, the protective effect was solely and consistently associated with development of nonseminoma. In summary, the data reported by mothers suggest that increased physical activity decreases the risk of TGCT (nonseminoma), although the data reported by sons do not substantiate this protective effect. Future studies of childhood physical activity should seek to validate responses further using recorded information sources such as school records.