New research suggests that infertile men are twice as likely to develop breast cancer as men without fertility problems.
The study also found that among those diagnosed with breast cancer, there were significantly more men without children.
Scientists from the Institute of Cancer Research, London (ICR) suggest the results suggest more work is needed to understand the underlying causes of male breast cancer – something that is largely unknown.
Study author Dr. Michael Jones, Senior Scientist in Genetics and Epidemiology at the ICR, said: “These are important findings linking infertility and breast cancer in men.
“Our study suggests that infertile men are twice as likely to develop breast cancer as men without fertility problems.
“The reasons for this association are unclear and there is a need to investigate the fundamental role of male fertility hormones in male breast cancer risk.
“We hope this could lead to insights into the underlying causes of male and possibly even female breast cancer.”
He added, “Breast cancer is often thought of as something that only affects women, but men can also be diagnosed with the disease.”
The new study, from the Breast Cancer Now Male Breast Cancer Study, looked at 1,998 men newly diagnosed with the disease in England and Wales over a 12-year period.
Around 370 men are diagnosed with breast cancer each year in the UK and because breast cancer in men is rare, research into the disease is usually limited to a small number of patients.
By studying a larger group of men, the team was able to show a statistically significant association between infertility and the risk of invasive breast cancer in men.
The men were asked if they had biological children, if they or their partners had ever had problems conceiving, or if they had consulted a doctor or clinic for fertility problems.
The researchers directly compared the fertility of the men with breast cancer to that of 1,597 men with no history of the disease.
While the biological reason is unclear, they discovered that men diagnosed with breast cancer were more likely to report fertility problems.
dr Simon Vincent, Director of Research, Support and Influence at Breast Cancer Now said: “Discovering a link between infertility and male breast cancer is a step forward in our understanding of male breast cancer and how we might find more ways to diagnose and treat men treat – and possibly women – with this devastating disease.
“Most importantly, we hope that the knowledge we have gained from this study will reach more men who could benefit from being educated about male breast cancer.”
Dave from Bristol was a police officer for 22 years before retiring to start his own IT company.
The 64-year-old was diagnosed with breast cancer in 2015. He has since had a mastectomy, treatment and is now in good health but is still on medication to reduce the chance of the cancer returning.
Dave said: “I was on holiday in Florida celebrating my birthday when I found a lump on my breast in the shower.
“It wasn’t painful and I didn’t tell anyone about it because life just seemed normal.
“I wasn’t aware that men should be screened for breast cancer, but I know that if your body is changing, you shouldn’t leave it, so I went to my GP as soon as I got home and he referred me to a specialist Advisor.
“Although I was told it was probably just a fat deposit, I had an ultrasound and a biopsy. A week later I was diagnosed with breast cancer. The tumor was the size of a golf ball.”
He added: “My mother died of ovarian cancer at the age of 68 and I knew there was a link between ovarian and breast cancer, but little is known about breast cancer in men in general.
“People will say, ‘I didn’t know men could understand that,’ and to be honest, I didn’t think I would ever understand that.”
The results are published in Breast Cancer Research.