Men who are diagnosed as azoospermic ( infertile because of an absence of sperm in their ejaculate ) are more prone to developing cancer than the general population, a study has found. And a diagnosis of azoospermia before age 30 carries an eight-fold cancer risk.
An azoospermic man's risk for developing cancer is similar to that for a typical man 10 years older.
The study was published in Fertility and Sterility.
Diagnoses of male infertility and azoospermia are surprisingly common in the United States. About 4 million American men, 15% of those ages 15-45, are infertile. Of these, some 600,000 ( about 1% of those of reproductive age ) are azoospermic.
Michael Eisenberg conducted most of the analysis using data gathered from the Texas Cancer Registry and the Baylor College of Medicine in Houston.
The study population consisted of 2,238 infertile men who were seen at a Baylor andrology clinic from 1989 to 2009. Their median age was 35.7 when they were first evaluated for the cause of their infertility. Of those men, 451 had azoospermia, and 1,787 did not. There were otherwise no apparent initial differences between the two groups.
Azoospermia can arise for two reasons. Obstructive azoospermia is caused by a blockage that prevents otherwise plentiful, fit sperm produced in the testes from reaching the ejaculate. But a screen of about one-fourth of the azoospermic men in the study population indicated that the vast majority suffered from the non-obstructive variety.
After undergoing a semen analysis, the men were followed for an average of 6.7 years to see which of them turned up in the Texas Cancer Registry. Their rates of diagnosed cancer incidence were then compared with age-adjusted cancer-diagnosis statistics of Texas men in general.
In all, a total of 29 of the 2,238 infertile men developed cancer over a 5.8-year average period from their semen analysis to their cancer diagnosis. This contrasted with an expected 16.7 cases, on an age-adjusted basis, for the male Texas population in general. This meant that infertile men were 1.7 times as likely to develop cancer as men in the general population. This is considered a moderately increased risk.
But comparing the cancer risk of azoospermic and nonazoospermic infertile men revealed a major disparity. The azoospermic men were at a substantially elevated risk, nearly three times as likely to receive a diagnosis of cancer as men in the overall population. Infertile men who weren't azoospermic, in contrast, exhibited a statistically insignificant increased cancer risk of only 1.4 times that of men in the overall population.
By excluding men whose cancer diagnosis came within two or three years of their infertility evaluation, the researchers were able to rule out the possibility that azoospermia caused by an undiagnosed cancer had affected the statistics.
While the study wasn't large enough to delineate which specific types of cancer pushed azoospermic men's incidence rates up, the diagnoses they received covered a wide range of cancers: brain, prostate and stomach tumors, as well as melanoma, lymphoma, testicular cancer and cancer of the small intestine. The findings suggest that genetic defects that result in azoospermia may also broadly increase a man's vulnerability to cancer, supporting the notion that azoospermia and cancer vulnerability may share common genetic causes.
The study, which was funded by the National Institute for Child Health and Human Development, is the first to examine the cancer risk of azoospermia in particular, or to link it to non-germ-cell cancers. Previous studies have failed to consistently identify any increased risk for nontesticular cancers in infertile men, whether azoospermic or otherwise. In those previous studies, however, azoospermic men couldn't be separately examined because sperm analyses weren't available.
Most striking of all was the cancer risk among azoospermic men who first had their semen analyzed before age 30. They were more than eight times as likely to subsequently develop cancer than Texas males in the general population of the same age. In contrast, there was no relationship between age of semen analysis and risk of cancer for nonazoospermic men. ( Xagena )
Source: Stanford University Medical Center, 2013