A number of hormonal approaches for prevention of endometrial and breast
cancers have been proposed. Because of the hormonal responsiveness of both
tumors, much attention has focused on effects of exogenous
hormone use. Although
estrogens in
hormone replacement therapy increase the risk of
endometrial cancer, the disease is substantially reduced by long-term use of
oral contraceptives. The issues with
breast cancer are more complex, mainly because of a variety of unresolved effects. Long-term
estrogen use is associated with some increase in
breast cancer risk, and certain patterns of
oral contraceptives appear to predispose to early-onset disease. With respect to
estrogens, preventive approaches for both
tumors would include use for as limited periods of time as possible. Addition of a
progestin appears to lower
estrogen-associated
endometrial disease, but its effect on
breast cancer risk remains less clear. Additional studies on effects of detailed usage parameters should provide useful insights into etiologic mechanisms. Other preventive approaches for
endometrial cancer that may work through hormonal mechanisms include staying thin, being physically active, and maintaining a
vegetarian diet.
Breast cancer risk may possibly be reduced by extended periods of breastfeeding, restriction of intake of alcoholic beverages, remaining thin later in life, and being physically active. Additional research is needed to clarify the
biologic mechanisms of these associations. The bridging of epidemiology with the biologic sciences should clarify many unresolved issues and lead to better preventive approaches.