Calcium excretion in metastatic prostatic carcinoma.

In 64 men with prostatic carcinoma, calcium excretion per litre of glomerular filtrate (Cae) was persistently lower in those with bone secondaries than in those with soft tissue involvement only, despite a normal range of serum calcium in both groups. In three patients who showed an improvement in their bony metastases on bone scan 6 months after starting treatment, the Cae values had increased slightly but still remained in the low range. In a further five who showed no improvement on bone scan, Cae values were lower than before. In patients with prostatic carcinoma, Cae is an indicator of early changes in calcium homeostasis. It may also provide an objective indication of progression of bone secondaries.