A single plasma sample method to assess disease activity in patients with bone metastases from carcinoma of the...

A single blood sample method was used to measure total skeletal activity during routine radionuclide bone scans in 114 patients with known carcinoma of the prostate. The method is based on the measurement of radioactivity in plasma after administration of 99mTc MDP and 51Cr EDTA, providing an assessment of total skeletal activity independent of renal function. The results showed a significant elevation of skeletal activity in patients with untreated bone metastases when compared with patients with no metastatic spread. Significant elevation with increasing extent of metastases was also shown, the highest activity being in patients with diffuse metastatic spread (superscan). Patients with treated metastatic disease showed significantly lower skeletal activity than patients with untreated bone metastases. The method requires the use of two radiopharmaceuticals injected as a mixture and potential errors may arise from pharmaceutical instability. In addition, elevation of total skeletal activity may be caused by coexistent metabolic bone disease. The results suggest that the measure may provide quantitative information in the assessment of the activity of bone metastases from prostatic carcinoma.