Bachground. Stage IV hormone-sensitive breast cancer is often treated with aromatase inhibitors (anastrozole, letrozole, exemestane), which block the conversion of dehydroepiandrosterone (DHEA) to estrone and estradiol. This is intended to obviate the need for steroid replacement and antiquate adrenalectomy. Methods. Patients who underwent oophorectomy and were being treated with new aromatase inhibitor therapy received serial measurements of serum estrone, estradiol and DHEA-sulfate (DHEA-S). Steroid values during responsive and progressive phases of disease were compared. In vitro, human breast cancer cell lines T-47D (estrogen-receptor and progesterone-receptor positive and HCC 1937 (estrogen-receptor and progesterone-receptor negative) were treated with DHEA-S. Proliferation rates were measured by colorimetric assay. Results. Disease in 12 of the 19 patients progressed. DHEA-S was less than 89 μg/dL in patients during the responsive phase and more than or equal to 89 μg/dL during disease progression, with 1 exception (P < .0005). Estrone and estradiol remained suppressed. After disease progression, the condition of 9 patients stabilized with aminoglutethimide therapy (n = 8) or adrenalectomy (n = 1), and their DHEA-S levels were reduced to less than 89 μg/dL. In vitro, elevated DHEA-S induced cell proliferation in T-47D cells. Conclusions. DHEA-S levels more than or equal to 89 μg/dL predicted disease progression in states of low estrogen. Tissue culture results supported the role of DHEA-S as an estrogenic agent. Oophorectomies with either aminoglutethimide therapy or adrenalectomy were effective remedies for breast cancer progression due to high DHEA-S.
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