Hormonal
therapy of
breast cancer is widely used and effective. Although never curative in advanced disease, significant palliation and durable remissions can be obtained with a wide variety of hormonal manipulations. Historically, surgical ablation was used to reduce endogenous
hormone levels, but this invasive procedure has been largely supplanted by drugs that reduce
hormone secretion or block
steroid hormone activity. A number of such antagonists are available, with
tamoxifen probably the most widely used. Response can also be achieved with
hormone agonists.
Estrogens and
androgens or their congeners have about the same level of activity as surgical ablation or
drug antagonists (20% to 30% overall response rate). The
progestins, another class of agonists, are also effective in the palliation of advanced
breast cancer.
Megestrol acetate, in part because of its oral formulation, is probably the most commonly used progestational
drug for the treatment of
breast cancer. Reports of 16 trials involving 1,342 patients show a response rate of 26% in patients with advanced
breast cancer treated with
megestrol acetate. The
drug has proved active in a small number of male patients and, in randomized trials, it has been shown to be comparable with
tamoxifen in efficacy (30% response for
megestrol acetate v 35% for
tamoxifen). Studies are currently under way to evaluate the possibility that high doses of
megestrol acetate may increase response rates, and to determine whether
weight gain, a well-described effect of this
drug, may prove beneficial in
cancer treatment.