Breast cancer risk during hormone therapy: experimental versus clinical data.
Author(s): Ruan X, Seeger H, Mueck AO.
Affiliation(s): Department of Gynecological Endocrinology, University of Beijing, Beijing, China.
Publication date & source: 2012, Minerva Endocrinol. , 37(1):59-74
Evidence is increasing suggesting that adding progestogens to estrogens can
increase the risk of breast cancer. However, our experimental data as a result of
scientific collaboration between university of Tuebingen, Germany, and university
of Beijing, China, comparing all available progestogens used in hormone therapy
and hormonal contraception present high evidence that there may be differences
regarding breast cancer risk. Especially of concern may be to differentiate
between primary and secondary risk i.e. between the effect of on benign and
malignant breast epithelial cells suggesting differences in primary risk and risk
in patients after breast cancer. Of importance also is that in contrast to
natural progesterone the apocrine impact of stromal growth factors and also
certain cell components of breast epithelial cells can strongly increase
proliferation rates of some (but not all. synthetic progestogens which can lead
to clinical cancer before (in contrast to estrogen-only therapy.
carcinoprotective mechanisms can work. Regarding clinical data, epidemiological
studies and especially the Women's Health Initiative, so far the only prospective
placebo-controlled study, demonstrate an increased risk under combined
estrogen/progestogen-, but not under estrogen-only therapy. However, up to now
the clinical studies cannot discriminate between the various progestogens mostly
due to too small patient numbers in the subgroups, and in most studies either
medroxyprogesterone acetate or norethisterone have been used. However, there is
evidence that the natural progesterone and dydrogesterone, possibly also the
transdermal usage of synthetic progestogens, may have less risks, but this must
be proven in further clinical trials.
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