Tamoxifen Breakthrough a Bitter Pill to Swallow [National Cancer Institute]
Mitchell, Penni, Herizons
Should healthy women be prescribed drugs to reduce one type of cancer, but be esposed to other health risks in the process?
This question sums up the controversy surrounding a National Cancer Institute study that hailed the cancer drug tamoxifen as a preventive treatment for women believed to be at high risk of getting breast cancer.
The Washington-based organization called off the study a year early because researchers considered it a 'breakthrough,' but breast cancer activists are questioning whether giving symptomless women a drug known to cause diseases is an ethical means of prevention.
The study involved 13,000 women believed to be high risk because of their postmenopausal status, family history of breast cancer or their diagnosis of having 'precancerous' cells. About 10 percent of the subjects were Canadian. Half of the subjects were given tamoxifen; half a placebo.
Among the 6,500 taking tamoxifen, the breast cancer rate was 1.3% ; in the control group of 6,500 it was 2.3% . There were 69 more breast cancers diagnosed among the placebo group, about 45% more than the tamoxifen group.
You'd think that if anyone would be excited about the news that tamoxifen might prevent breast cancer, it would be Nora Gambioli, executive director of the Canadian Breast Cancer Network, a consumer advocacy organization keen on research aimed at cancer prevention. Its board members are all breast cancer survivors; many have taken tamoxifen at some point.
"This is not a cure," Gambioli says, adding that the Network's directors are "very cautious" about the preliminary results (they haven't been published in a peer-reviewed journal).
At the time the trial was stopped, five women taking the placebo had died of breast cancer, but five had also died in the tamoxifen group: three from breast cancer and two from blood clots in the lungs.
A total of 17 women taking tamoxifen in the NCI study developed pulmonary embolisms, compared to 6 in the control group. Yet oncologists involved in the study referred to the tamoxifen-linked diseases as 'side effects' and said that benefits of taking tamoxifen clearly outweighed the risks. One sensitive surgeon remarked 'even aspirin can kill you.'
As well, tamoxifen users also had over twice the rate of uterine cancer -- .5% [33 cases] compared to .2% [14 cases] as women in the control group. The tamoxifen link to uterine cancer is well-known; in fact, the Hamilton Regional Cancer Centre pulled out of the study because it didn't want to put women at risk. …