Abstract
Objectives: Postmenopausal hormone therapy (PMH) has been widely used by menopausal women living
in western countries for the past several decades. Numerous studies have evaluated
the relationship between PMH and breast cancer risk because steroid hormones have
been implicated in breast cancer etiology. Methods: A review of selected studies was performed to evaluate the history of investigations
of the association between PMH and breast cancer, with a focus on studies evaluating
different PMH regimens and different histologic types of breast cancer. Results: Though studies conducted before the early 1990s suggest that both combined estrogen
and progestin (E + P) PMH and unopposed estrogen (E) PMH are associated with an increased
risk of breast cancer, more recent observational studies suggest that E + P, particularly
current use for 5 years or longer, is more strongly associated with breast cancer
risk than is unopposed E. Results from the Women’s Health Initiative (WHI) randomized
trials have confirmed these findings as they indicate that E + P is causally related
to breast cancer (relative risk (RR) = 1.24; 95% confidence interval (CI): 1.01–1.54),
while E alone is not (RR = 0.77; 95% CI: 0.59–1.01). Conclusions: There is clear and consistent evidence that use of E + P increases a woman’s risk
of breast cancer. Alternatively, current evidence suggests that use of unopposed E
is not as strongly associated with breast cancer risk. Further studies are needed
though to examine how different PMH regimens, doses, and methods of delivery are related
to breast cancer risk, and how PMH impacts the risks of different types of breast
cancer.
Keywords
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Article info
Publication history
Accepted:
May 11,
2004
Received in revised form:
April 15,
2004
Received:
December 16,
2003
Identification
Copyright
© 2004 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.
