(October 30, 2008 - Insidermedicine) Hot flushes, night sweats, or joint symptoms may be signs that hormone disrupting drugs used to treat hormone receptor-positive breast cancer are working, according to research published in The Lancet Oncology.

Here is some information on breast cancer and hormones:

•    Some types of breast cancer are hormone sensitive, meaning that they grow in response to the presence of estrogen or progesterone.

•    Drugs that block the activity of hormones have been developed to treat breast cancer. These are known as endocrine therapies.

•    Endocrine therapies can produce symptoms similar to those that women experience during menopause.

Researchers out of Cancer Research UK and Queen Mary's School of Medicine and Dentistry in London looked at the relationship between the side effects of treatment and recurrence rates of breast cancer among women treated for hormone-positive breast cancer with one of two endocrine therapies: tamoxifen or anastrazole.

After three months, 37% of women reported experiencing symptoms of hot flushes or night sweats, and 31% reported joint symptoms. After nine years, cancer recurred in only 18% of women with hot flushes and night sweats and 14% of women with joint symptoms, compared with 23% of women who did not have these side effects.

Today’s research suggests that some side effects of endocrine therapy may actually be associated with lower cancer recurrence rates, a fact that may encourage women suffering from these side effects to stick with treatment.