Jan. 21, 2000 (Lake Worth, Fla.) -- Two Canadian researchers say there seems to be a correlation between frequent strenuous activity during the teen years and testicular cancer. But experts who reviewed the study for WebMD say that there is no evidence adolescent boys should cut back on exercise.
The Canadian researchers, Anil Srivastava and Nancy Kreiger, MD, sent out a survey to more 200 men who had been diagnosed with testicular cancer and asked a number of questions relating to recreational exercise, occupational exercise, diet, marital status, years of schooling, household income, smoking habits, and height and weight. Out of this survey, the researchers found what appeared to be a significant associated risk between frequent moderate (more than five times a week) to strenuous recreational activity during the teen years and testicular cancer.
From their results, published in the current issue of the American Journal of Epidemiology, Srivastava and Kreiger theorize that this associated risk factor could possibly be due to several factors. They suggest a rise in hormone level during physical activity may have more of an effect on younger men than on older, or that testicular trauma associated with some sports such as cycling and horseback riding may cause the increase risk. Their final hypothesis is that muscle mass is associated with higher androgen (male sex hormone) production. They point to androgen levels in relation to prostate cancer for support.
"That hasn't been shown to be true for prostate cancer, so that is why I doubt this paper," says Joseph R. Wagner, MD, who reviewed the study for WebMD. Wagner is physician in charge of the urology/oncology department at Beth Israel Medical Center in New York.
Still, Srivastava and Kreiger conclude in their paper, "Important insights might also be gained from further investigation of the relation between hormone levels and physical activity, particularly with respect to frequency of exercise."
Wagner and Craig Nichols, MD, who was also asked to comment on the study, see major flaws in the study design.
"They just cast a broad net and something came out," Nichols explains. "Statistically that will happen if you ask enough questions -- something will be significant." Nichols is professor of medicine at Oregon Health Sciences University and a leading authority on testicular cancer.
Wagner says that a better-designed study might indeed give credence to the researchers' claim, but he feels that based on this study, high school athletes needn't cut back on activity.
"Are you going to tell all these young men not to exercise?" Wagner asks. "There's probably greater risk in that than for getting testicular cancer. The prevalence of [testicular cancer] is only 0.5 in 100,000."
The known risk factors for testicular cancer are undescended testicles and a family history of the disease. Too much exercise, on the other hand, is so far not supported by the body of medical literature, say Nichols and Wagner.
WebMD contacted Kreiger's office and was told that she would not comment on either the study or Nichols' and Wagner's comments.
- A new study shows that there may be an association between frequent, moderate exercise during the teen-age years and the development of testicular cancer later in life.
- Researchers claim that a rise in male hormone levels or testicular trauma could explain the increased risk.
- Two outside experts question the design of the study, and say that young men should continue to exercise, since the absolute risk of testicular cancer is so low.