Radioimmunoassay of bone marrow prostatic acid phosphatase.

The clinical value of prostate acid phosphatase (PAP) measurements in the bone marrow aspirate of patients with prostatic adenocarcinoma has been unclear. Using a radioimmunoassay (RIA) to measure PAP, we have evaluated this potential indicator of occult metastases in 127 controls and in 300 patients with prostatic adenocarcinoma. Elevations of the tumor marker were found in 9%, 10%, 19%, and 82% of patients with stages B, C, D1, and D2 adenocarcinoma respectively. Clinical follow-up ranging from 7 to 43 months (average 23 months) was available for 97 patients without any initial indication of metastasis by bone scan. In this group 11 patients had elevated levels of bone marrow acid phosphatase (BMAP) by RIA and four developed radiological evidence of bone metastasis 21-25 months following initial staging. However, only three of the 86 patients with normal BMAP levels have developed bone metastasis. Our results indicate that measurement of bone marrow PAP by immunological methods has prognostic significance. Dilution of the bone marrow aspirate by peripheral blood, however, may limit the application of this technique.