Combined Estrogen and Testosterone Therapy Increases Breast Cancer Risk

Combined estrogen and testosterone therapy significantly increases the risk of invasive breast cancer in women, according to a study published in the Archives of Internal Medicine. Researchers at Harvard University analyzed data from the Nurses' Health Study, a prospective cohort study involving postmenopausal women. Over a 24-year period, 4,610 incident cases of invasive breast cancer were identified among postmenopausal women. The study found that women with a natural menopause who used estrogen plus testosterone therapies had a nearly 2.5-fold greater risk of breast cancer compared to those who never used postmenopausal hormone therapies.

Key Takeaways:

• The risk of breast cancer associated with current use of estrogen and testosterone therapy was significantly greater compared to estrogen-only therapy.
• Women receiving postmenopausal hormone therapies with testosterone had a 17.2% increased risk of breast cancer per year of use.
• The risk of invasive breast cancer was nearly 2.5-fold greater among current users of estrogen plus testosterone therapies compared to never users of postmenopausal hormone therapies.
• The study involved a prospective cohort study of postmenopausal women over a 24-year period, with 4,610 incident cases of invasive breast cancer identified.
• The study found a significant increase in breast cancer risk among women with a natural menopause using estrogen and testosterone therapies.
• The risk of breast cancer was marginally greater among women using estrogen and progesterone therapy compared to estrogen and testosterone therapy.

Statistics:

• 4,610 incident cases of invasive breast cancer were identified among postmenopausal women over a 24-year period.
• The study involved 1,359,323 person-years of follow-up.
• Women with a natural menopause using estrogen and testosterone therapies had a 2.48-fold greater risk of breast cancer compared to never users of postmenopausal hormone therapies.
• The risk of breast cancer was increased by 17.2% per year of use among women receiving postmenopausal hormone therapies with testosterone.

Sources:

• Tamimi, R.M. et al. (2006) Combined estrogen and testosterone use and risk of breast cancer in postmenopausal women. Archives of Internal Medicine, 166(14), 1483-1489.
• American Medical Association (Publisher).