Breast cancer cells can have oestrogen receptors or progesterone receptors. Most male breast cancer cells do have hormone receptors. This is known as being hormone receptor positive. About 9 out of 10 male breast cancers (90%) are oestrogen receptor positive, which means that they need oestrogen in order to grow. Your specialist will arrange tests on your cancer cells when you are first diagnosed. This shows if the cancer cells have hormone receptors. Men have small amounts of oestrogen in their body. Hormone therapies block oestrogen from making cancer cells grow. So they can reduce the chance of the cancer coming back.
The most common hormone therapy for male breast cancer is tamoxifen. The side effects are much the same as in women. Tamoxifen can make you feel sick when you first start taking it, but this usually wears off quite quickly. The most common side effect for men and women is hot flushes. Tamoxifen may also cause weight gain, difficulty sleeping, low mood and depression. In men, tamoxifen may also cause a loss of sex drive. This has been reported in up to 3 out of 10 men taking tamoxifen.
Other hormone therapies are used to treat breast cancer, including aromatase inhibitors. Large studies have shown that aromatase inhibitors reduce the chance of breast cancer coming back in women who have had their menopause, but we need more research before we know how well aromatase inhibitors work in men.