Breast Cancer Treatment: Weighing the Hormonal Options
Tamoxifen has been the standard in hormonal breast cancer treatment for decades. But newer treatments are challenging tamoxifen's superiority.
Three in Five Breast Cancers Fueled by Estrogen
Breast cancer is the second biggest cancer killer of women in
the industrialized world, taking the lives of about 40,000 women each year in
the U.S. alone. More than 211,000 new cases will be diagnosed.
About three in five of these women have tumors that are fueled
by the hormone estrogen, making hormone therapy to stop this growth a
cornerstone of regimens to prevent recurrences and improve survival.
While tamoxifen prevents estrogen from acting on tumors,
aromatase inhibitors actually block an enzyme the body uses to make
estrogen, thereby slashing the body's production of estrogen altogether.
The new studies suggest that this different mechanism of action
to decrease estrogen levels may mean that aromatase inhibitors may shrink
tumors better and longer with fewer side effects, doctors say.
Femara Study Halted Early
Goss says the drug was so effective that an international
committee decided to disclose the results early in order to offer the drug to
all women in the trial.
The international trial pitted Femara against placebo in nearly
5,200 women following five years of tamoxifen therapy. Four years after the
start of the study, cancer came back in 13% of the women on placebo but only in
7% of those on Femara.
Anderson, who as a patient of Goss was invited to participate
in the study, tells WebMD that the day the trial was stopped early was
"very exciting. I found out I had been on Femara for the last two years,
indicating to me that my chances of recurrence had been cut in half."
Arimidex Beats Out Tamoxifen
In the Arimidex trial, women who switched to the aromatase
inhibitor fared better than if they stayed on standard tamoxifen.
The study followed 448 postmenopausal women who had been taking
tamoxifen for at least two years following breast cancer surgery. The women
were randomly assigned to continue taking tamoxifen or switch to Arimidex for
By three years later, cancer was 64% less likely to recur in
the group of women who switched to Arimidex, the study showed
Other Hormonal News
Those were not the only studies on the new hormonal treatments
Yet another trial showed that women who took Arimidex instead
of tamoxifen were slightly less likely to see their cancer recur after four
years compared with those who took tamoxifen.
And in another study of nearly 300 women, those who took
Arimidex were significantly more likely to become candidates for
breast-conserving surgery than those who took standard tamoxifen, says Ian
Smith, MD, of Royal Marsden Hospital in London.
And in the one trial that pitted Femara against Arimidex, those
on Femara were slightly less likely to respond. But there was no difference in
the amount of time it took for the cancer to grow.
Finally, the largest study ever to evaluate a hormonal therapy
for women with advanced breast cancer showed that those on Femara stayed free
of disease longer than those on tamoxifen.