Tamoxifen is NOT a Preventative Medicine

AstraZeneca, the manufacturer of Tamoxifen is paying researchers to try to prove its contention that Tamoxifen could be used as a "preventive medicine" for all women and all types of breast cancer. The news headlines tend to overstate the benefits and grossly understate the life-threatening risks of this drug. AstraZeneca's latest propaganda effort, published in January 2003, is a review of the results of 3 previous Tamoxifen breast cancer prevention trials. It claims that "The Tamoxifen prevention trials showed a 38% reduction in breast cancer incidence." (Lancet 2003; 361:296-300)

Tamoxifen is NOT a preventive medicine. It is a synthetic estrogen-like drug with many serious side effects. It has only been found to block the growth of tumors that are estrogen-receptor positive. In June 2002, the FDA made AstraZeneca add WARNINGS to the physician information about Tamoxifen that listed newly discovered risks of the drug. Serious, life-threatening or fatal events associated with Tamoxifen include endometrial cancer, uterine sarcoma, stroke, and clots in the lungs.

The review of all of the Tamoxifen breast cancer prevention trials shows that the death rate from all causes is 230% higher in the Tamoxifen group than in the placebo group (25 vs 11; p=0·028). Endometrial cancer was 220% higher in the Tamoxifen group than the placebo (11 vs 5; p=0·2) and blood clotting events were 250% higher with Tamoxifen (43 vs 17; p=0·001), particularly after surgery.

Research has also shown that women who take Tamoxifen after a 1st breast cancer are 5 times more likely to develop a more difficult to treat estrogen receptor-negative cancer in their other breast than women who did not take Tamoxifen (Journal of the National Cancer Institute 2001;93:1008-1012,963-).

In spite of these reports AstraZeneca continues to pay its researchers to try prove its usefulness as a "Preventive Medicine." Two of the principal investigators of the study, J. Cuzick and J. Forbes, admit that they have a serious conflict of interest, since they receive significant funding from AstraZeneca, the manufacturer of Tamoxifen. Both men are principal investigators in multiple trials for which their institutions receive funding from AstraZeneca and both have served as occasional consultants and advisory board members to AstraZeneca. This conflict of interest could easily create a bias that could compromise the integrity and validity of the conclusions they propose.

The good news is that since 1997, several studies have shown that diet and exercise can reduce breast cancer risk by anywhere from 10 to more than 60 percent. Just this month, German researchers reported that women who reported the highest levels of cycling exercise have a 34% reduced risk of developing breast cancer of all types (Am J Epidemiol 2003 Jan 15;157(2):121-30).

We can't prevent all cancer, but the 1997 American Institute for Cancer Research report estimates that with healthier lifestyles we could prevent up to 60 percent of all cancers, including 33 to 50 percent of breast cancer cases. Eating a mostly plant-based diet that is focused primarily around vegetables, fruits and whole grains, with smaller portions of meat, is at the heart of this cancer-prevention strategy. Limiting alcohol and maintaining a healthy weight, not only through exercise,but also portion control and healthy food choices are the most effective preventive medicines we have.

The bottom line, "Don't Do Drugs!" A preventive medicine should be just what it says it is, something other than a medicine. Diet and exercise work better than drugs in preventing breast cancer and have none of the life-threatening side effects.