Men with naturally high levels of the female hormone estrogen may have a greater risk of developing breast cancer, according to research by an international collaboration published in the Journal of Clinical Oncology (2015; doi:10.1200/JCO.2014.59.1602).
This is the first time a link between estrogen levels in the blood and male breast cancer has been identified, despite its connection to breast, uterine, and ovarian cancers in women.
Men with the highest levels of estrogen were two and a half times more likely to develop breast cancer than men with the lowest levels of the hormone.
Breast cancer in men is very rare, occurring approximately 100 times less often than it does in women. The lifetime risk for men is an estimated 1 in 1,000, according to the American Cancer Society.
The research at the National Cancer Institute in the United States was part of an international collaboration between Cancer Research UK, the National Cancer Institute, and others.
The aim was to study a large international pool of men with breast cancer. The research compared estrogen levels in 101 men who went on to develop breast cancer with 217 healthy men.
“We’ve shown for the first time that just like some forms of the cancer in women, estrogen has a big role to play in male breast cancer,” said study author Professor Tim Key, PhD, Cancer Research United Kingdom’s hormone and nutrition expert at the University of Oxford. “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 estrogen in their blood. Our discovery is a crucial step forward in understanding the factors behind male breast cancer.”
The symptoms, diagnosis, and treatment of male breast cancer are very similar to breast cancer in women. The main risk of developing the disease in men is age; almost eight in 10 cases occur in those age 60 years and older.
“Breast cancer in men isn’t discussed very often, so a diagnosis can be a big shock for the small group of men who develop the disease,” said Julie Sharp, MD, head of health information at Cancer Research UK.
“Some of the estrogen 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.
“This early research is crucial in understanding why these men [develop] breast cancer, so that one day we can treat it more effectively.”