Long-Term
Follow-Up Determines Continued Superiority of Arimidex ®
over Nolvadex ®
According to a recent article published in the journal Cancer,
long-term follow-up indicates that Arimidex ® (anastrozole)
continues to be superior over Nolvadex ® (tamoxifen)
in the treatment of early-stage, hormone-positive breast
cancer in postmenopausal women.
Breast cancer is the second leading cause of cancer death
in women in the United States, with approximately 200,000
cases diagnosed each year. Depending on the extent of the
cancer, some women may benefit from adjuvant therapy. Adjuvant
therapy is a treatment that is added to increase the effectiveness
of a primary therapy. Adjuvant therapy may include chemotherapy,
radiation therapy, biologic therapy or hormonal therapy. These
adjuvant treatments can be administered alone or in combination
after surgery to increase the chances of curing the cancer
or prolong a remission.
Nolvadex ® (tamoxifen) is a hormonal agent used to treat
certain types of breast cancer. Breast cancer cells that are
stimulated to grow by the female hormones estrogen and/or
progesterone are referred to as hormone-positive breast cancer.
For years, Nolvadex ® was the standard hormonal agent given
to women with hormone-positive breast cancer. Nolvadex ®
works by blocking estrogen receptors, thereby preventing estrogen
stimulated growth of the hormone-positive breast cancer cells.
Arimidex ® (anastrozole) is a hormonal agent called an
aromatase agent that has been recently approved for the treatment
of ER-positive, postmenopausal breast cancer. Arimidex ®
produces anti-cancer effects by blocking the formation of
estrogen. Clinical trials have been underway to compare Arimidex ®
to Nolvadex ® in patients with different stages of hormone-positive
breast cancer.
Researchers from the Arimidex ®, Tamoxifen Alone or in
Combination Trialists? Group conducted a clinical trial to
directly compare Arimidex ® to Nolvadex ® when used
as single agents, as well as in combination, as initial hormonal
therapy for post-menopausal, ER-positive breast cancer. Initial
results demonstrated superior outcomes for patients treated
with Arimidex ® compared to Nolvadex ®. Updated results
from this trial continue, to determine long-term outcomes
in each group of patients. The study involved 9,366 postmenopausal
women with early invasive breast cancer. All participants
had undergone surgery with or without chemotherapy and/or
radiation therapy. Patients were randomly selected to receive
either Arimidex ® alone (3,125 women), Nolvadex ® alone
(3,116 women) or Arimidex ® plus Nolvadex ® (3,125 women)
combined on a daily basis for five years or until breast cancer
recurred.
At an average follow-up of 4 years, Arimidex ® continues
to demonstrate superior outcomes compared to Nolvadex ®.
Cancer-free survival at 4 years was 87% for patients treated
with Arimidex ®, and 84.5% for those treated with Nolvadex ®.
In addition, time to cancer recurrence was greater for those
treated with Arimidex ®, and the development of breast
cancer in the opposite breast was almost half that rate compared
to the group treated with Nolvadex ®. Updated side effect
analysis confirmed earlier analyses: Nolvadex ® produces
a higher incidence of uterine cancer, vaginal bleeding, stroke,
blood clots and hot flashes, while Arimidex ® produces
a higher incidence of musculoskeletal disorders and bone fractures.
The updated results of the ATAC trial indicate that Arimidex ®
remains superior to Nolvadex ® in the treatment of hormone-positive,
early breast cancer in postmenopausal women. However, due
to the differences in side effects, it is important for every
patient to speak with their physician about their individual
risks and benefits of treatment with either agent.
Reference: The ATAC (Arimidex, tamoxifen alone or in combination)
trialists? group. Anastrozole alone or in combination with
tamoxifen versus tamoxifen alone for adjuvant treatment of
postmenopausal women with early-stage breast cancer. Cancer.
2003;98:1802-1810.
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