Comparative value of bone scintigraphy and radiography in monitoring tumor response in systemically treated prostatic carcinoma.

Radionuclide bone scans and skeletal radiographs were obtained before and during combination chemotherapy or initial hormonal treatment in 46 patients with disseminated adenocarcinoma of the prostate. The purpose of the study was to determine the usefulness of these two modalities in evaluating tumor response to therapy. Prior to treatment, bone scans were positive in 44 patients (96%). In all but one patient either bone radiographs or bone marrow biopsy revealed evidence of osseous metastases. In 22 patients partial response to therapy was documented by a variety of other staging tests. Eleven of these patients showed concurrent or later improvement on bone scans; one showed improvement on a radiograph. "Flare phenomena" were observed relatively frequently since 23% of the scans and 50% of the radiographs showed worsening at the time of response. Bone scans revealed worsening in 79% of 33 patients with disease progression of extraosseous tumor; radiographs were equally sensitive (82% worsening). It is concluded that bone scans in particular are useful for monitoring tumor status in systemically treated patients with prostate cancer. However, because of the lack of sensitivity for response and paradoxical worsening with tumor regression in some patients, scans are not accurate enough to be employed as the sole test in following these patients.