London - Men who struggle to become fathers are up to 64 percent more likely to get prostate cancer, a major study has found.
Research on nearly 1.2 million men showed those who underwent fertility treatment had a "remarkably high" chance of developing the cancer compared with those who had children naturally.
Scientists said men who require fertility treatment should be carefully monitored for the disease in later years. They stressed this was particularly the case for those who take part in ICSI – a form of IVF in which sperm is injected directly into an egg.
Experts said infertility was a "canary in a coal mine" that could give an early warning of other problems. They believe the genetic faults that cause it are also likely to be behind developing cancer.
Researchers tracked 1.18 million Swedish fathers whose children were born from 1994 to 2014.
Those who had gone through with ICSI – an intra-cytoplasmic sperm injection used for men with low quality sperm or a low count – were 64 percent more likely to develop prostate cancer. Men who took part in conventional IVF, where sperm is placed in a lab dish with an egg, had a 33 percent greater chance of prostate cancer.
Men needing fertility treatment also developed the cancer earlier. They were 86 percent more likely to get it before the age of 55 with ICSI, while the figure was 51 percent with IVF.
Despite the increased relative risk, the numbers of those getting prostate cancer remained low – just 0.42 percent of ICSI men compared with 0.28 percent of "natural" fathers. The difference of 50 percent rose to 64 percent when age and other risk factors were taken into account.
The research team came from Lund University in Sweden and Stanford University in the US.
Writing in the British Medical Journal, they said: "The main conclusion of this study, comprising virtually all men fathering a child in Sweden during two decades, is that men who achieved fatherhood through assisted reproduction had a remarkably high risk of prostate cancer."
The researchers suggested men needing fertility treatment should be tested earlier for the disease.
Professor Allan Pacey, a men’s health expert at Sheffield University, hailed the new study as "excellent", adding it followed earlier research showing "male infertility might serve as a 'canary in the coal mine' for men’s health that both men and their doctors should be better attuned to."