SEATTLE-A group of breast cancer patients treated with tamoxifen
(Nolvadex) outside of clinical trials had up to a 60% reduction
in their risk of developing cancer in the contralateral breast
and no increased risk of ovarian or endometrial cancer, report
Linda S. Cook, PhD, and her colleagues at the Fred Hutchinson
Cancer Research Center.
The study provides reassurance about the safety of short-term
tamoxifen therapy in conventional medical practice, but since
the average duration of tamoxifen treatment was less than 2 years
in this group, the results shed no light on possible adverse effects
from long-term use.
The Seattle researchers used cancer registry and medical record
data to identify a cohort of 12,598 women in western Washington
state under age 85 who were diagnosed with primary breast cancer
between 1978 and 1990. Of these, 39 women developed ovarian cancer,
42 endometrial cancer, and 234 contralateral breast cancer prior
The case subjects who had developed the second primary cancers
were matched by age, disease stage, and year of initial breast
cancer diagnosis with control subjects drawn from the same cohort.
The percentage of women who had received tamoxifen was 10% and
18%, respectively, among contralateral breast cancer subjects
and controls; 18% and 20%, respectively, among ovarian cancer
subjects and controls; and 26% and 31%, respectively, among endometrial
cancer subjects and controls (J Natl Cancer Inst 87:1359-1364,
The overall reduction in risk for contralateral breast cancer
with any use of tamoxifen was 50%, with reductions of 60% seen
for women who used the agent for more than 1 year and for those
who continued therapy through the end of study follow-up or stopped
therapy less than 1 year before the end of follow-up.
Risk reductions were larger in post-menopausal than in premenopausal
women, although the data suggest that tamoxifen use of more than
1 year's duration reduces the risk in premenopausal women as well.