ER
Status in Initial Breast Cancer Strongly Associated with ER
Status in Contralateral Breast Cancer
According to a recent article published in the Journal of
the National Cancer Institute, estrogen receptor (ER) status
of an initial breast cancer is strongly associated with ER
status in subsequent breast cancer in the contralateral breast.
A significant portion of women with breast cancer has ER-positive
breast cancer. ER-positive breast cancer refers to a type
of breast cancer that is stimulated to grow from the naturally
occurring female hormone estrogen. Women with ER-positive
breast cancer often receive hormone therapy as a component
of their therapeutic regimen. Hormone therapy, typically consisting
of tamoxifen (Nolvadex ®) or aromatase agents, inhibits
the growth-stimulatory effects of estrogen on cancer cells.
Women diagnosed with ER-positive breast cancer who are treated
with tamoxifen also have a significant reduction in the risk
of developing a breast cancer in the other (contralateral)
breast.
Researchers from Pennsylvania and Ohio recently conducted
a clinical study to evaluate the association between ER status
with initial breast cancer and ER status in subsequent contralateral
breast cancer. The study included data from 5,513 patients
who were diagnosed with breast cancer and were involved in
the National Surgical and Adjuvant Breast and Bowel Project
trials B-18, B-22, and B-25. Of these patients, 176 developed
contralateral breast cancer. All patients in these trials
who were over the age of 50 years were treated with tamoxifen,
regardless of ER status, and patients under the age of 50
did not receive tamoxifen. Among the group of patients who
did not receive tamoxifen and developed a contralateral breast
cancer, 89% of those with an ER-positive initial breast cancer
had an ER-positive contralateral breast cancer, and 70% of
those with an ER-negative initial breast cancer had an ER-negative
contralateral breast cancer. Among the group of patients who
did receive tamoxifen and developed a contralateral breast
cancer, only 56% of those with an ER-positive initial breast
cancer developed an ER-positive contralateral breast cancer,
while 78% of those with an ER-negative initial breast cancer
developed an ER-negative contralateral breast cancer.
The researchers concluded that an ER-positive status of an
initial breast cancer is strongly associated with the same
ER status in a contralateral breast cancer in patients who
are not treated with tamoxifen and ER-negative status of an
initial breast cancer is strongly associated with the same
status in contralateral breast cancer. However, patients with
an initial ER-positive breast cancer appear to have a reduced
incidence of ER-positive contralateral breast cancer, indicating
an overall reduction in contralateral breast cancer in patients
with ER-positive breast cancer who are treated with tamoxifen.
Clinical trials are currently underway to evaluate the use
of aromatase agents in the prevention of breast cancer. It
is important for patients with breast cancer to discuss the
risks and benefits of tamoxifen or aromatase agents with their
physician.
Reference: Swain S, Wilson J, Mamounas E, et al. Estrogen
receptor status of primary breast cancer is predictive of
estrogen receptor status of contralateral breast cancer. Journal
of the National Cancer Institute. 2004; 96:516-523.
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