Aromatase Inhibitors now for breast cancer prevention.

A new option for breast cancer prevention has just been presented at the American Society of Clinical Oncology in Chicago and printed online in the New England Journal of Medicine.

Results of the MAP.3 (Mammary Prevention.3 trial) demonstrated a 65% reduction in breast cancers in women who were high risk and took the aromatase inhibitor exemestane (Aromasin) each day.

The planned 5 year study enrolled 4500 women in the US, Canada, Spain and France.  They reported at an average follow-up of 3 years at the meeting.  The women were all postmenopausal with one or more of the following risk factors: 60 years of age or older, Gail risk of >1.66, prior biopsy revealing atypical ductal or lobular hyperplasia, lobular carcinoma in-situ (LCIS), or prior treatment of contralateral DCIS by mastectomy.

After only 3 years of follow-up, the treated group demonstrated a 65% reduction in invasive breast cancers: the exemestane group of 2285 women had only 11 cancers but 32 cancers were reported in the placebo group of 2275 women.

Adverse symptoms such as hot flashes, fatigue, sweats, and joint aches were reported in 88% of the treated group and 85% of the placebo group.  So far no adverse cardiovascular events, clots, or nonbreast cancers have been reported.  Long-term use of any aromatase inhibitor leads to bone loss, which shows up later.

This adds a third prescription drug to our breast cancer prevention armamentarium, each with a slightly different rate of prevention and side effect profile.  Tamoxifen is the only drug approved for the premenopausal woman and raloxifene (Evista) is approved to both preserve bone density and reduce breast cancer.  The decision to pursue drug prevention is obviously a complicated one for anyone to make in thoughtful consultation with a breast specialist.

Other measures, such as weight control and exercise, apples, aspirin, omegas, that we have discussed and others that we will discuss, are appealing because they apply to almost everyone, don't require consultation and have a lower side effect profile.


As a disclaimer, I report that I am a faculty resource for Eli Lilly who makes Evista.