New
Drug Shows Promise Against Advanced Breast Cancer
Exemestane Holds
Off Recurrence Longer Than Tamoxifen
The first head-to-head
comparison of the drugs tamoxifen and exemestane in women
with advanced breast cancer shows the latter was not only safe,
it also improves disease-free survival.
Exemestane, one of
a class of drugs called aromatase inhibitors, is currently approved
for women whose cancer progressed while they were taking tamoxifen.
Two other aromatase inhibitors are also approved in the US -
letrozole and anastrazole.
"We're probably moving
into a transition phase where we will be using these types of
drugs over tamoxifen in the near future," says Dr. Jay Brooks,
chief of hematology/oncology at the Ochsner Clinic Foundation
in New Orleans.
Studies
Show Exemestane Success
This latest study
comes just days after another clinical trial showed the superiority
of taking tamoxifen and exemestane sequentially for five years,
as opposed to taking tamoxifen alone for the full five years.
The results of these
and other studies mark a step forward in the evolution of breast
cancer treatment, experts say.
"[Exemestane] will
be a good choice for metastatic disease," says Dr. Robert Paridaens,
lead author of the study who presented his findings at the Fourth
European Breast Cancer Conference in Hamburg, Germany.
"If someone asks me
is there a subgroup where it's absolutely a must to start with
exemestane, I would say the high-risk patients who are estrogen-receptor-positive
who already have a metastasis," he says.
For postmenopausal
women with estrogen-receptor-positive breast cancer, the gold
standard has been to take tamoxifen for five years after initial
treatment for the tumor.
Tamoxifen, which has
been available for 20 years, works by interfering with
the ability of estrogen to fuel tumor growth.
While many women do
benefit from tamoxifen, others fail to respond and, in general,
the drug seems to lose its effectiveness after about five years,
experts say.
Tamoxifen and exemestane
both block the growth of breast tumors that respond to estrogen,
but the two drugs work in different ways. Tamoxifen interferes
with the ability of breast cancer cells to use estrogen for
growth, whereas exemestane interferes with the body's ability
to make estrogen.
Aromatase inhibitors
may be poised to take the place of tamoxifen. As their name
implies, these compounds inhibit aromatase, an enzyme that helps
make estrogen. Exemestane is actually slightly different from
the other two medications in that it has a "steroidal structure."
One interesting finding
in the study, according to Dr. Paridaens, is that there
is no adverse affect on patients' lipid profiles, compared to
what has been found in studies of non-steroidal aromatase inhibitors.
The new study, sponsored
by drug maker Pfizer, involved 382 patients from 81 medical
centers in 25 countries. The women were randomly selected to
receive either tamoxifen or exemestane, but the study was an
"open label" one, meaning both physicians and patients knew
who was taking which drug.
The researchers wanted
to see if exemestane would increase progression-free survival
by three months over tamoxifen. In fact, the results were slightly
better than that.
Women in the exemestane
group had a median progression-free survival of 10.9 months
compared with 6.7 months for those in the tamoxifen group.
Exemestane also led
in other categories. Among the women receiving exemestane, 7.4
percent responded completely to the treatment, versus 2.6 percent
of the tamoxifen patients. Also, 36.8 percent of the exemestane
participants responded partially to treatment, compared to 26.6
percent in the tamoxifen group.
Physicians
Look at Best Use for Patients
Although a number
of questions still need to be answered, including how long a
woman should take exemestane, the drug does seem poised to take
its place alongside tamoxifen, even perhaps instead of it, experts
say.
How quickly this happens
will depend, in part, on whether insurers are willing to reimburse
patients for the drug. Exemestane is more expensive than tamoxifen,
experts say.
"The question of the
future would be does tamoxifen have any role to play in an adjuvant
setting? We don't know," Dr. Paridaens says. In any event, the
spectrum of medications for breast cancer survivors is expanding.
"The number of drugs we have at our disposal is increasing.
It's fantastic," he adds.
Always consult your
physician for more information.
Online
Resources
(Our Organization
is not responsible for the content of Internet sites.)
American
Cancer Society
American
Society for Clinical Oncology
Centers
for Disease Control and Prevention (CDC)
National
Cancer Institute
National
Cancer Institute Exemestane Study
National
Institutes of Health (NIH)
National
Women's Health Information Center
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May 2004
New
Drug Shows Promise Against Advanced Breast Cancer
Studies
Show Exemestane Success
Physicians
Look at Best Use for Patients
Blocking
Hormone Effects
Preventing
Hormone Production
Online
Resources
Blocking Hormone Effects
Hormone therapy is
used to prevent the growth, spread, and recurrence of breast
cancer. The female hormone estrogen can increase the growth
of breast cancer cells in some women.
Hormones are chemicals
produced by glands, such as the ovaries and testicles. Hormones
help some types of cancer cells to grow, such as breast cancer
and prostate cancer. Hormone therapy may be considered for women
whose breast cancers test positive for estrogen or progesterone
receptors.
A hormone receptor
test measures the amount of certain proteins (called hormone
receptors) in cancer tissue.
Hormones (such as
estrogen and progesterone that naturally occur in the body)
can attach to these proteins. If the test is positive, it indicates
that the hormone is probably helping the cancer cells to grow.
In this case, hormone
therapy may be given to block the way the hormone works and
help keep the hormone away from the cancer cells (hormone receptors).
If the test is negative,
the hormone does not affect the growth of the cancer cells,
and other effective cancer treatments may be given.
An antiestrogen drug
frequently used, called tamoxifen (Nolvadex®), blocks the
effects of estrogen on the growth of malignant cells in breast
tissue.
However, tamoxifen
does not stop the production of estrogen. Side effects that
may occur when taking tamoxifen include hot flashes, nausea
or vomiting, vaginal spotting, fatigue, headaches, and skin
rash.
Taking tamoxifen also
increases the risk of endometrial cancer (involves the lining
of the uterus) and uterine sarcoma (involves muscles of the
uterus), both cancers of the uterus. There is also a small risk
of blood clots and stroke.
A second antiestrogen
drug under study for breast cancer prevention, called Raloxifene®,
is not recommended for women who have already been diagnosed
with breast cancer.
Preventing
Hormone Production
Drugs recently approved
by the US Food and Drug Administration (FDA),
called aromatase inhibitors, are used to prevent the recurrence
of breast cancer in postmenopausal women.
These drugs, such
as anastrozole (Arimidex®) and letrozole (Femara®),
prevent estrogen production.
Anastrozole is effective
only in women who have not had previous hormonal treatment for
breast cancer.
Letrozole is effective
in women who have previously been treated with tamoxifen. Possible
side effects of these drugs include osteoporosis or bone fractures.
Another new drug for
recurrent breast cancer is fulvestrant (Faslodex®).
Also approved by the
FDA, this drug eliminates the estrogen receptor.
This drug is used following previous antiestrogen therapy. Side
effects for fulvestrant include hot flashes, mild nausea, and
fatigue.
Another means of stopping
the production of estrogen is the use of surgery to remove the
ovaries in women who have not gone through menopause, called
an oophorectomy.
Always consult your
physician for more information.
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