Changes in the blood chemistry of patients with disseminated carcinoma of the breast during endocrine therapy

A patient with metastatic prostate cancer is described where treatment with Adriamycin (doxorubicin) and estramustine produced severe hypophosphatemia (serum phosphate level, 1.2 mg/dl), which was reversible when treatment was discontinued. Previous studies have shown no effect of Adriamycin on serum phosphate levels. A retrospective study of serial serimm chemistry values was done in 15 patients treated with estramustine. A significant fall in the serum phosphate level (mean, 0.8 f 0.3 mg/dl) was observed during the first 6 weeks of treatment. When compaired with similar patients treated with bilateral orchiectomy, estramustine-treated patients had lower levels of serum calcium, fractional excretion of calcium, serum phosphate, and renal tubular threshold for phosphate reabsorption (TmPO,/GFR). Qualitatively similar but quantitatively smaller effects were also seen in a group of patients treated with diethylstilbestrol (DES) in a dose of 1 to 3 mg daily. Estrainustine appears to have significant effects on bone mineral metabolism, particularly on renal phosphate handling resulting in significant hypophospha-temia. This is probably due to an estrogenic effect. Cancer 58:2208-2213, 1986. STRAMUSTINE PHOSPHATE IS AN ORAL AGENT used E in the treatment of prostate cancer.'-6 It is a conjugate of estradiol 17p and an alkylating agent (mechlor-methamine). The precise mode of action of the drug is not Estramustine has been reported to produce responses in 10% to 35% of patients with metastatic pros-tate cancer no longer responsive to conventional hormone treatment." Toxicity is similar both qualitatively and quantitatively to that of diethylstilbestrol (DES) and includes nausea and vomiting, gynecomastia, fluid retention, thrombo-phlebitis, and occasional elevation of liver function tests. It is believed that estramustine owes part of its therapeutic action and toxicity to a high-dose estrogen effect.' For the past several years, we have treated patients with advanced (Stage D) prostate cancer whose disease is resistant to conventional hormone treatment with estra-mustine, either alone or in combination with Adriamycin (doxorubicin). In one patient, severe hypophosphatemia developed that was reversed only with discontinuation of

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