Infertile men are almost three times more likely to develop testicular cancer than fertile men, US research suggests.
Over the past decade, rates of testicular cancer and male infertility have risen steadily throughout the western world.
However, it has been unclear whether the two trends are related to each other.
For this latest study, researchers explored the link using data from 22,562 male partners from couples who were seeking fertility treatment between 1967 and 1998.
Almost a quarter of the men, 4,549, had male factor infertility. This was based on a clinical presentation of abnormal semen.
The men were linked to the California Cancer Registry and were studied between 1998 and 2004 for any signs of testicular cancer.
The rate of testicular cancer among the men in the study was compared with the rate among healthy men, matched for age, in the general population.
Overall, a total of 34 of the men were diagnosed with testicular cancer at least one year after seeking treatment for infertility.
Of the 34 men, 86 per cent developed seminomas, 12 per cent non-seminomas and 2 per cent unspecified disease.
Men who underwent fertility treatment were 1.3 times more likely to develop testicular cancer than men who did not undergo treatment.
After controlling for other risk factors, men with male factor infertility were 2.8 times more likely to develop the cancer than men without the condition.
The research team, led by Dr Thomas Walsh from the University of California, proposed that faulty DNA repair, as well as environmental factors, may contribute to both testicular cancer and infertility.
But they stressed that it is 'highly improbable' that infertility treatment itself may be a risk factor for testicular cancer.
'It is also unlikely that the results represent a screening phenomenon in which men who seek treatment for infertility are diagnosed with a previously unrecognised cancer because of diagnostic testing,' they added.
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