Men with infertility may be at higher risk of some cancers

Men with severely reduced fertility have a greater likelihood of developing certain non-reproductive cancers, new research suggests.

Researchers in Sweden have reported an increased risk of colorectal and thyroid cancers in men who used ICSI to become fathers, compared to those who conceived naturally. Previous studies have associated reduced male fertility with poorer long-term health outcomes such as diabetes, cardiovascular disease, metabolic disorders, urological cancers and shorter life expectancy.

'Reproductive capacity is linked to an individual's genetic makeup,' said Dr Angel Elenkov of Lund University, senior author of the study published in the European Journal of Epidemiology. 'One theory is that if something goes wrong at the genetic level – which can manifest as reduced sperm quality – other systems in the body may also be affected, increasing the risk of disease.'

To explore the possible link between reduced male fertility and non-reproductive cancer risk, the authors first identified 1,137,829 men who became first-time fathers between 1994 and 2014. This involved comparing data from the Medical Birth Register (MBR), which records almost every birth in Sweden, to the Multi-Generation Register, a national database linking individuals to their parents.

Information on conception was then obtained from the MBR and Swedish National Quality Registry for Assisted Reproduction. Of these men, 20,142 conceived through standard IVF and 14,540 used ICSI, while 1,103,147 conceived naturally. Groups were then cross-referenced against the Swedish Cancer Register.

The study reported a higher risk of some non-reproductive cancers among men who became fathers through ICSI compared with those who conceived naturally. This increased risk was not observed in the standard IVF group.

'They were found to have almost twice the risk of developing colorectal cancer and three times the risk of thyroid cancer,' said co-author Michael Kitlinski, a medical student at Lund University. 'It has previously been found that men with severely reduced fertility are at increased risk of developing testicular and prostate cancer. That is why we wanted to investigate whether there is also a link to other forms of cancer.'

The authors noted that lifestyle factors may have contributed to the associations observed in the study: for example, smoking, alcohol consumption and obesity are linked with various cancer types as well as poorer semen quality (see BioNews 1297). However, information on potential confounding variables, including paternal smoking habits and body mass index, was not available in the registry datasets and therefore not considered.

The researchers have also suggested that their results further support consideration of disease-preventive approaches in men seeking healthcare for fertility issues.

'These findings are important from a public health perspective given that cancers of the colon and rectum, as well as thyroid cancer, are on the rise among younger people,' said Dr Elenkov. 'These cancers could be prevented through early screening.'