A new study has found that premenopausal women who had elevated blood levels of the androgens testosterone or androstenedione or low levels of progesterone had an increased risk of breast cancer. The study was published in the Journal of the National Cancer Institute.

Sex steroids have been implicated in the development of breast cancer. Studies have shown that postmenopausal women who have elevated blood levels of androgens of adrenal and/or ovarian origin or of estrogens have an increased risk of breast cancer. Studies of premenopausal women, however, have produced unclear results.

To examine the relationship between premenopausal blood concentrations of sex steroids and subsequent breast cancer risk, Dr. Rudolf Kaaks, of the International Agency for Research on Cancer in Lyon, France, and colleagues conducted a case-control study of 370 case subjects (premenopausal women with breast cancer) and 726 control subjects (premenopausal women without breast cancer) drawn from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.

Elevated blood concentrations of testosterone, androstenedione, and an adrenal androgen were associated with an increased risk of breast cancer, whereas elevated blood concentrations of progesterone were associated with a decreased risk of breast cancer. Breast cancer risk was not associated with blood levels of other hormones.

The estimated absolute risk of breast cancer among women younger than age 40 after 10 years of follow-up was 2.6% for those in the highest quartile of blood testosterone versus 1.5% for those in the lowest quartile and 1.7% for those in the highest quartile of blood progesterone versus 2.6% for those in the lowest quartile.

SOURCE:
Journal of the National Cancer Institute, May 18, 2005