Largest
Analysis To Date Faslodex ® as Effective as Arimidex ®
as Hormone Therapy in Metastatic Breast Cancer
According to a recent article published in the journal Cancer,
Faslodex ® (fulvestrant) appears at least as active as
Arimidex ® (anastrozole) in the treatment of hormone-positive
metastatic breast cancer that has stopped responding to initial
hormone therapy.
Over 200,000 new cases of breast cancer are diagnosed annually
in the United States, causing approximately 40,000 deaths
every year. Fortunately, patients undergoing recommended screening
procedures have a higher rate of early detection of the disease,
ultimately improving chances of survival. Newer therapeutic
agents are also extending survival for patients who have metastatic
breast cancer, in which the cancer has spread to distant sites
in the body and is often difficult to cure. Historically,
Nolvadex ® (tamoxifen) was the most commonly used hormone
therapy for breast cancer, but recently, new hormonal agents
called aromatase agents have been approved for the treatment
of hormone receptor-positive breast cancer and have expanded
the arsenal of effective therapy for patients with this disease.
Hormone receptor-positive breast cancer, referred to as estrogen
receptor and/or progesterone receptor-positive cancer, is
a type of cancer that is stimulated to grow by naturally occurring
female hormones called estrogen and/or progesterone. Estrogen
receptor-positive (ER-positive) breast cancer cells have an
overabundance of specific proteins, called estrogen receptors.
Circulating estrogen binds to these receptors, facilitating
the growth of the cell. In addition, the binding of estrogen
to estrogen receptors stimulates the synthesis of progesterone
receptors inside the cell. For patients with progesterone
receptor-positive (PR-positive) breast cancer, progesterone
that binds to the progesterone receptors also facilitates
cellular replication. Currently, many women with ER and/or
PR-positive breast cancer are treated with drugs that either
inhibit estrogen synthesis in the body or block estrogen from
causing growth-stimulatory effects.
Faslodex ® is a new anti-estrogen agent and achieves anti-cancer
effects through a different mechanism than other approved
hormonal therapies. First, when Faslodex ® binds to the
estrogen receptors, estrogen is crowded out and no longer
able to bind to these receptors. Second, Faslodex ® degrades
the estrogen receptors to which it is bound. Both of these
mechanisms prevent cancer cells from accessing sufficient
amounts of estrogen needed for cellular growth and replication.
The Food and Drug Administration (FDA) has approved Faslodex ®
for hormone treatment in postmenopausal women with hormone-positive
breast cancer that has failed previous hormone therapies.
Arimidex ® is an aromatase agent that has also been recently
approved by the FDA for treatment of hormone-positive breast
cancer. Arimidex ® exerts anti-cancer effects by inhibiting
an enzyme called aromatase which is responsible for a step
in the conversion process during which the active form of
estrogen is formed. Clinical trials have been ongoing to compare
different hormone agents to determine optimal therapeutic
strategies.
Two multi-institutional clinical trials have recently been
conducted to directly compare Faslodex ® to Arimidex ®
in the treatment of metastatic hormone-positive breast cancer.
The two trials combined included over 850 postmenopausal women
who had stopped responding to prior hormone therapy, primarily
Nolvadex ®. The overall anti-cancer response rates were
19.2% and 16.5% for patients treated with Faslodex ® and
Arimidex ®, respectively. In patients who responded, the
average duration of response was 16.7 months for those treated
with Faslodex ® and 13.7 months for those treated with
Arimidex ®. Both treatments were well tolerated; however,
significantly fewer side effects affecting the joints occurred
in patients treated with Faslodex ®.
The researchers concluded that Faslodex ® is at least
as effective as Arimidex ® in the treatment of hormone-positive
advanced breast cancer in postmenopausal women who have stopped
responding to prior hormone therapy. Patients with advanced,
hormone-positive breast cancer may wish to speak with their
physician about the risks and benefits of treatment with Faslodex ®
or Arimidex ® or the participation in a clinical trial
further evaluating hormone therapy or other novel therapeutic
approaches. Two sources of information regarding ongoing clinical
trials include the National Cancer Institute ( cancer.gov)
and www.cancerconsultants.com. Personalized clinical trial
searches on behalf of patients are also performed by cancerconsultants.com.
Reference: Robertson J, Osborne K, Howell A, et al. Fulvestrant
versus anastrozole for the treatment of advanced breast carcinoma
in postmenopausal women. A prospective combined analysis of
two multicenter trials. Cancer. 2003;98:229-238.
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