Scientists discover three new genetic variants linked to male breast cancer
The study was funded by Breast Cancer Now and Queen’s University Belfast and has been published in the Journal of the National Cancer Institute.
While breast cancer in men is very rare, around 370 men are diagnosed with the disease every year in the UK (compared to 55,000 women who are diagnosed) and around 80 men lose their lives each year.
Men with a strong family history of breast cancer among female relatives are known to be at greater risk, and around 10% of male cases are caused by mutations in the BRCA2 gene. The exact causes of the disease in men are not yet understood, and, for years, there has been considerable debate about whether male and female breast cancer are distinct from one another.
The study looked at 1,380 men with breast cancer, primarily from the Breast Cancer Now Male Breast Cancer Study. The researchers first identified three common variations in DNA (known as ‘SNPs’) that predispose men to developing breast cancer, bringing the total now known number to five.
The researchers then analysed over 170 SNPs known to affect risk in women, finding significant overlap in the genetic risk factors for the disease in men.
The results found male and female breast cancer may have a very similar genetic basis ― a discovery which could in future lead to new preventive treatments for men and women.
The study also found that men at the highest genetic risk were almost four times more likely to develop breast cancer than those at lowest risk. The three genetic changes, called rs9371545, rs554219 and rs78540526, were found to increase the risk of developing breast cancer in men by approximately 47%, 45% and 61% respectively.
Lead author Dr Nick Orr, from The Patrick G. Johnston Centre for Cancer Research at Queen’s University Belfast, said: “There has been much debate about whether breast cancers which occur in women and men are distinct from one another. Our study has shown, for the first time, that the genetic factors influencing susceptibility to male breast cancer and the most common type of female breast cancer are much more alike than they are different.
“This suggests that the underlying biological processes which affect breast cancer initiation and progression are probably similar in men and women, so that advances in prevention and treatment for the disease may be of benefit to all patients, irrespective of their gender.”
Dr Simon Vincent, Director of Research, Services and Influencing at Breast Cancer Now, which funded the study, said: “This study, which shows more of a similarity between the genetic causes of the disease in men and women than previously thought, is a major step forward. Our knowledge of breast cancer in men is limited, because male breast cancer is rare which makes it difficult to collect enough tissue or blood samples to research and understand the disease. Research like this is critical to improving our understanding of the disease in men and we hope the Breast Cancer Now Male Breast Cancer Study will continue advancing our knowledge.
“We now look forward to further research into the shared genetic causes of male breast cancer which could lead to developing risk reducing treatments and interventions to help prevent more cases among those at increased risk in the future.
“Breast cancer in men is much rarer than the disease in women, but it is vital men are aware of the signs and symptoms, and know what to do should they notice a change. Anyone who has questions or concerns about male breast cancer can call our free Helpline on 0808 800 6000 for support and information. Our nurses are just at the end of the phone.”
It is hoped that the discovery of new locations in the genome linked to male breast cancer could now enable scientists to identify the biological mechanisms that cause the disease to develop in men, and could ultimately lead to the development of new preventive drugs for those at high risk.
While further research would be needed, the authors also suggest the findings could in future help to develop more precise risk testing for men carrying BRCA2 mutations, enabling them to understand whether they are at additional or lower risk due to other genetic changes, which could help guide decisions around any risk-reducing steps.