Benefits and Risks of Tamoxifen are Similar in African American and White Women
African American and white women with breast cancer have the same
risks of getting cancer in the other breast and of getting blood
clots while on the drug tamoxifen, according to a study in the December
1, 2004 Journal of the National Cancer Institute by scientists at
the National Cancer Institute (NCI), part of the National Institutes
of Health. The benefits of tamoxifen, including protection against
cancer in the second breast (contralateral breast cancer), have
been demonstrated in previous studies whose subjects were predominantly
Tamoxifen stops or slows the growth of cancer cells in the breast
by interfering with the activity of estrogen, a hormone some breast
cancers need to grow. Chemotherapy and tamoxifen are given to women
with early stage breast cancer to treat cancer cells throughout
the body and to prevent the cancer from coming back. Tamoxifen can
also prevent contralateral breast cancers. Large trials have shown
that women with early stage breast cancer who are treated with this
drug for five years have a 47 percent reduced rate of contralateral
But these studies have also shown a small increase in the number
of blood clots in women taking tamoxifen, especially when it is
taken during chemotherapy. Blood clots can be deadly, leading to
strokes, for example, or blocking the lungs' supply of blood from
the heart. Worta McCaskill-Stevens, M.D., the study's lead author
and medical oncologist in the NCI's Division of Cancer Prevention,
said, "There have been concerns about the association of blood
clots with tamoxifen because while few data exist on the effects
of tamoxifen on African American women, greater rates of obesity
and cardiovascular disease in this population leave them more vulnerable
to blood clots than white women."
For their study, McCaskill-Stevens and her colleagues at the National
Surgical Adjuvant Breast and Bowel Project (NSABP) analyzed data
from 13 clinical trials of tamoxifen performed by the NSABP. On
their own, none of these studies included enough African American
women for scientists to determine whether tamoxifen affects them
differently. Together, these trials include 20,878 women, of whom
1,842 are African American. The NCI scientists did two analyses
of the data: one to determine the rates of contralateral breast
cancer, the other to determine rates of blood clot-related events.
Because of evidence that tamoxifen is primarily effective in treating
estrogen receptor positive breast cancers-cancers whose cells have
a surface protein that estrogen can attach to-McCaskill-Stevens'
group included only women with this kind of cancer in their analysis
of contralateral breast cancer rates. This group included 10,619
women. Race had no effect on the rate of contralateral breast cancers.
For their study of the incidence of blood clot-related events,
the researchers analyzed data from all 20,878 women in the trials.
Again, race had no effect on the risk of these events.
Body mass index was a risk factor for both contralateral breast
cancer and blood clots. Age was associated with an increased risk
of blood clots while the number of lymph nodes infiltrated by cancer
cells increased the risk of contralateral cancers. The latter is
contrary to previous studies, most of which have shown no such association.
Based on these results, McCaskill-Stevens said, "African American
and white women appear to have the same risks of breast cancer and
blood clots in response to tamoxifen." She believes their data
demonstrate "the need to assess an individual woman's health
and personal history to determine the benefits and risks of prescribing
tamoxifen to prevent breast cancer."
For more information about cancer, please visit the NCI Web
site at http://www.cancer.gov
or call NCI's Cancer Information Service at at 1-800-4-CANCER (1-800-422-6237).