Earlier this summer, the National Institutes of Health decided not to fund a breast cancer prevention trial to test Letrozole (Femara), an aromatase inhibitor, vs. raloxifene (a tamoxifen-like drug) in the primary prevention of breast cancer. Expert Patient PJ Hamel first wrote about the canceled breast cancer chemoprevention study in June, when the story first became news. More recently, Tara Parker-Pope, a wonderful science writer for the Wall Street Journal, covered the issues surrounding the canceled National Surgical Adjuvant Breast and Bowel Project (NSABP) study brilliantly.
Chemoprevention and Clues from the ATAC Trial
In my eyes this is a minor tragedy. In one sense, I feel the answer may already be out there. In the ATAC trial of tamoxifen vs. Arimidex in the adjuvant setting, there were fewer new breast cancers in the women who received Arimidex than tamoxifen - a rate of about 0.31% per year in the arimidex group vs. 0.5% in the tamoxifen group. This would imply superiority as a chemopreventive drug for the aromatase inhibitor Arimidex. Chemoprevention, as defined by the NCI, is "the use of drugs, vitamins, or other agents to try to reduce the risk of, or delay the development or recurrence of, cancer."
Breast Cancer Prevention Trial in Women with DCIS
Another chemoprevention trial being conducted in Europe is comparing Arimidex vs. tamoxifen in the prevention of breast cancer in women with ductal carcinoma in situ. Again I would expect the aromatase inhibitor (i.e. Arimidex) to show superiority as it had in the ATAC trial. If so, these two trials alone might convince me to offer an aromatase inhibitor as a chemopreventive agent. In that regard, the head of the NCI might be justified in saving his limited budget for translational and molecular biology research.
How Popular is Chemoprevention?
One problem, though, is that chemoprevention is probably underutilized. I have started women with DCIS and atypical ductal hyperplasia on tamoxifen; women at high risk of breast cancer who understand the risks and benefits of chemoprevention have also been offered tamoxifen and some have chosen to take it. I am a huge fan of cancer prevention (I take an aspirin a day based on my belief it may prevent prostate and colon cancer). Many clinicians and patients have embraced this idea.
Others have not. The idea of a chemopreventive agent has not had universal appeal. Many patients, or people in the general public, will take a vitamin if they believe it will prevent illness. For example Vitamin E was thought to prevent heart disease - until the recent clinical trials showed that Vitamin E may actually increase the risk of heart disease compared to placebo. But the idea of taking a patented medicine like tamoxifen, or arimidex or letrozole (aromatase inhibitors made by different manufacturers) has not gained widespread acceptance. Funding this trial and seeing it through to its conclusion might have broadened the appeal for chemoprevention and saved many lives.