Switching
from Tamoxifen to Arimidex ® Improves Outcomes in Breast
Cancer
According to results recently presented at the 2003 San Antonio
Breast Cancer Symposium, switching to Arimidex ® after
at least 2 years of tamoxifen reduces the risk of cancer recurrences
compared to continued tamoxifen in postmenopausal women with
estrogen-receptor positive breast cancer.
Estrogen-receptor (ER) positive breast cancer refers to a
common type of breast cancer that is stimulated to grow by
the female hormone estrogen. One common component in the treatment
of ER-positive breast cancer is hormone therapy. Hormone therapy
works by reducing the levels of circulating estrogen in the
body or blocking the growth-stimulatory effects of estrogen
on cancer cells. Tamoxifen (Nolvadex ®) is an anti-estrogen
type that was the historical standard for ER-positive breast
cancer. Recently, however, new agents referred to as aromatase
agents have entered the clinical setting as treatment for
hormonal therapy for breast cancer and are rapidly gaining
momentum as agents used for hormone therapy. Patients responding
to tamoxifen are typically treated with the agent for 5 years.
Results from clinical trials have demonstrated that outcomes
are not improved with use of tamoxifen for over 5 years. In
addition, results from a recent clinical trial have indicated
that the use of the aromatase agent letrozole (Femara ®)
following 5 years of tamoxifen improves outcomes for patients
with ER-positive breast cancer.
Recently, researchers from Italy conducted a clinical trial
to compare the aromatase agent Arimidex ® (anastrozole)
to tamoxifen in patients already treated with tamoxifen. This
trial included over 400 postmenopausal women with ER-positive
breast cancer, who had already been treated with at least
2 years of tamoxifen. Patients then received either continued
tamoxifen for up to 5 years, or Arimidex ® for a comparable
duration of time. matched time. At an average follow-up time
of approximately 2-3 years, recurrence rates were reduced
by over 60% in the group of patients who switched to Arimidex ®,
compared to those who continued on tamoxifen. Longer follow-up
is necessary to determine if this will correlate with a significant
survival difference.
The researchers concluded that it appears that postmenopausal
women with ER-positive breast cancer switch to Arimidex ®
after at least 2 years of tamoxifen have a significantly reduced
rate of cancer recurrences. However, the authors cautioned
that larger clinical trials are necessary to confirm this
finding and advise this option as a standard approach to treating
cancer. Patients who are being treated with tamoxifen may
wish to speak with their physician about the risks and benefits
of switching over to Arimidex ®.
Reference: Boccardo F, Rubagotti A, Amoroso D, et al. Anastrozole
appears to be superior to tamoxifen in women already receiving
adjuvant tamoxifen treatment. Proceedings from the 2003 San
Antonio Breast Cancer Symposium. December 2003. Abstract #3.
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