Obesity could increase the risk of breast cancer in men, according to a new study.
The study bringing together data from around the world found that obesity, and several other physical and hormone-related characteristics are associated with increased breast cancer risk in men.
Around 400 men are diagnosed with breast cancer each year in the UK but the causes of male breast cancer are poorly understood, partly due to the fact that it so rare. Although genetic factors are involved, there have been indications for some time that certain physical and hormonal factors are also linked to risk, but uncertainty has remained because of the relatively limited patient numbers in individual studies.
The Male Breast Cancer Pooling Project brings results together from multiple studies being carried out around the world looking into the causes of the disease, including data from the largest male breast cancer study to date, funded by Breakthrough Breast Cancer. The size and scale of this robust project allows the team of international scientists to combine their findings and be more conclusive.
With latest findings published in the Journal of the National Cancer Institute (JNCI), the research team found that breast cancer risk in men increases with weight, and that being obese is associated with an increased risk of a man developing breast cancer of about 30%. Klinefelter syndrome, the presence of an extra X chromosome in men, was also confirmed to increase breast cancer risk, and there was an association with gynecomastia, the presence of enlarged breast tissue in men, which appeared to have an effect on risk, even separately from obesity.
Professor Anthony Swerdlow, Professor of Epidemiology at The Institute of Cancer Research, London, and lead of the UK arm of the study, said:
“This research brings together data from studies of male breast cancer from around the world to clarify risk factors that have been uncertain. The results suggest that men who are overweight may be at increased risk of male breast cancer.
“We know that body size can be related to hormone levels. Also, hormonal factors may be the reason why patients with Klinefelter syndrome, who have comparatively low levels of testosterone and high levels of oestrogen, have raised breast cancer risks compared with other men. Our results suggest the need to investigate further the role of sex hormones in causation of breast cancer in men.”
Dr Matthew Lam, Research Officer at Breakthrough Breast Cancer, said:
“We know that hormonal factors play a large part in increasing risk of breast cancer in women but how these factors affect risk in men is not well understood. This study provides new insight into the contributing role of sex hormone levels and physical conditions that control them in male breast cancer. Exploring this relationship further will be a next step for the Male Breast Cancer Pooling Project.
“We can’t currently predict which men will go on to develop breast cancer which is why Breakthrough is leading the way to find out more about this form of the disease through our research work. Researchers we fund have already found a gene, called RAD51B, which can cause breast cancer in men. This discovery could help to find new treatments for the disease and has also enabled us to learn more about how changes in the RAD51B gene can increase the risk of breast cancer in women.”