Breast cancer affects hundreds of men every year – and levels of the female hormone oestrogen may be a major cause of it, researchers report today.
The disease affects about 350 men a year in the UK.
The latest study shows that men with high levels of oestrogen are more than twice as likely to develop the disease as those with the lowest levels.
British researchers worked with the US National Cancer Institute on the project, which involved some 101 men with breast cancer – compared with 217 healthy men. The findings are reported in the Journal of Clinical Oncology.
Although oestrogen levels vary between men, they can also be boosted by body fat.
Researcher Professor Tim Key said: “We’ve shown for the first time that just like some forms of the cancer in women, oestrogen has a big role to play in male breast cancer. So now the challenge is to find out exactly what this hormone is doing to trigger this rare form of the disease in men, and why some men have higher levels of oestrogen in their blood.
"Our discovery is a crucial step forward in understanding the factors behind male breast cancer.”
Dr Julie Sharp, of Cancer Research UK, which backed the research, said: “Some of the oestrogen variation in men will simply be natural, but for others there may be a link to being overweight. Fat cells in the body are thought to drive up the body’s level of this hormone in men and women, so this is another good reason to try and keep a healthy weight."
Brinton et al. Prediagnostic sex steroid hormones in relation to male breast cancer risk. Journal of Clinical Oncology 11 May 2015; doi: 10.1200/JCO.2014.59.1602
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