ABSTRACT: Tamoxifen Therapy for Primary Breast Cancer and Risk
of Contralateral Breast Cancer
[07/04/2001; Journal of the National Cancer Institute]
Background: Women diagnosed with breast cancer have a twofold
to sixfold greater risk of developing contralateral breast cancer
than women in the general population have of developing a first
breast cancer. Tamoxifen therapy reduces this risk, but it is
unclear if this benefit exists for both estrogen receptor (ER)-positive
and ER-negative contralateral tumors.
Methods: Using data from a population-based tumor registry that
collects information on the ER status of breast tumors, we
followed 8981 women residing in western Washington State who
were diagnosed with a primary unilateral invasive breast cancer
during the period from 1990 through 1998 to identify cases of
contralateral breast cancer.
We restricted our analyses to women
who were at least 50 years old and whose first breast cancer
had a localized or regional stage; women who received adjuvant
hormonal therapy but not chemotherapy (n = 4654) were classified
as tamoxifen users, while those who received neither adjuvant
hormonal therapy nor chemotherapy (n = 4327) were classified
as nonusers of tamoxifen. By reviewing selected patient abstracts,
we estimated that 94% of the subjects were classified correctly with
respect to tamoxifen use.
The risk of contralateral breast cancer
associated with tamoxifen use was estimated with the use of Cox
regression. All statistical tests were two-sided.
Results: Of the 89 tamoxifen users and 100 nonusers of tamoxifen
diagnosed with contralateral breast cancer, 112 had ER-positive
tumors, 20 had ER-negative tumors, and 57 had tumors with an ER
status that was unknown or had not been determined by an
The risk of developing an ER-positive
and an ER-negative contralateral tumor among tamoxifen users
was 0.8 (95% confidence interval [CI] = 0.5 to 1.1) and 4.9
(95% CI = 1.4 to 17.4), respectively, times that of nonusers of
tamoxifen. This difference in risk by ER status was statistically
Conclusions: Tamoxifen use appears to decrease the risk of
ER-positive contralateral breast tumors, but it appears to
increase the risk of ER-negative contralateral tumors.
Ann's NOTE: I conclude that Tamoxifen benefits a very small number of women. Compare 89 breast cancers in those taking Tamoxifen versus 100 in those not taking it. Troublesome. As always, we need to KNOW who will benefit from a drug with so many adverse effects. PLEASE READ MUSA MAYER's REMARKS BELOW.
Read the AP report to see
what she means
Associated Press Article
Read Musa Mayer's Comments
New York Time's Version
Abstract # 525
NCI Press Release
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