By Jennifer Litton, M.D., assistant professor, Department of Breast Medical Oncology, MD Anderson Cancer Center
At ASCO, Canada's NCIC Clinical Trials Group released three-year results from a large randomized double-blind Phase III trial comparing Exemestane (Aromasin), an aromatase inhibitor, to placebo for postmenopausal women at high risk of developing breast cancer.
The study showed a 65% decrease in developing breast cancer when compared to placebo in high-risk, postmenopausal women.
Given how this drug works, it is only effective in women who are postmenopausal without ovarian estrogen production. Exemestane is a drug that has been used for years when treating women with early breast cancer and metastatic disease. Now, it may have another indication in preventing breast cancer.
This is not surprising, as we saw a decrease in second breast cancers that developed in the opposite breast in the early breast cancer trials from this class of drugs. Tamoxifen, which has been used in prevention for years, is a well-tolerated and very effective drug. However, only a small percentage of women choose to take the drug.
This may be due to the menopausal side effects such as hot flashes. But many are concerned about the very rare, but serious side effects of blood clots and uterine cancer. This may be of very minimal importance when we are treating breast cancer, but many healthy women may have reservations that the risk, although very low, is too high for them.
Exemestane and its cousin drugs have their own set of side effects that can include hot flashes, joint stiffness and pain, and vaginal changes that can include dryness and pain with sex, as well as bone loss.
I am eager to see further follow-up from this study, as well as the studies that will directly compare the aromatase inhibitors with tamoxifen. We also have more work to do to improve the number of cancers prevented, as well as preventing those breast cancers that are not fed by estrogens.
Three-year study results