Experts Raise Eyebrow at Link Between Exercise in Teen Years and Testicular Cancer
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
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.