Breast Cancer Prevention Study Focuses on Anti-Hormone Therapy

Researchers have long speculated that aromatase inhibitors (AIs), a class of drugs used to treat estrogen-driven breast cancer, could also prevent development of the disease in older women. New research presented at the annual San Antonio Breast Cancer Symposium this past December confirms that suspicion.

Results of the IBIS-II Prevention trial showed that after a median follow-up of five years, postmenopausal women at high risk for breast cancer who take the AI anastrozole could reduce their risk of developing the disease by half, which means that 2 percent of women on anastrozole would develop breast cancer over five years compared with 4 percent of women on the placebo. However, it is unknown if the AI can actually prevent deaths from breast cancer.

Participants who took anastrozole experienced a modest increase in musculoskeletal events.

Researchers were surprised to find that women taking anastrozole also experienced a reduction in developing other malignancies, such as skin, gastrointestinal and gynecologic cancers.

AIs work by blocking the enzyme aromatase from converting the hormone androgen into estrogen, but they can slightly increase the risk of muscle and joint pain, as well as bone mineral loss.