Decreased serum phosphate levels after high-dose estrogens in metastatic prostate cancer. Possible implications.

Hypophosphatemia and osteomalacia have been described in patients with metastatic prostate cancer. The mechanism of hypophosphatemia in prostate cancer is not known. A decrease in serum phosphate levels was observed in 16 of 18 patients with metastatic prostate cancer treated with high-dose diethylstilbestrol diphosphate. To determine if the fall in serum phosphate was indeed due to diethylstilbestrol diphosphate, the data from several similar groups of patients treated with chemotherapy and combined chemohormonal therapy that included diethylstilbestrol diphosphate were re-examined. Fifty-eight patients were treated with doxorubicin, doxorubicin plus cis-platinum, doxorubicin plus diethylstilbestrol diphosphate, or diethylstilbestrol diphosphate alone. A significant decrease in serum phosphate levels was seen only in patients treated with diethylstilbestrol diphosphate. Hypophosphatemia and possibly osteomalacia in metastatic prostate cancer may be related to estrogen therapy.