• prostate neoplasms;
  • bone metastasis;
  • bone scintigraphy


To assess the clinical usefulness of quantifying the extent of disease on bone scans in monitoring treatment response in patients with advanced prostate cancer, using computer-assisted image analysis.


The percentage of the positive area on the bone scan (%PABS) was quantified automatically using a personal computer with an image-analysis program. Serial measurements of %PABS in 42 patients with bone metastasis from prostate cancer followed for a mean (range) of 33 (4–72) months with hormonal therapy were compared with those of the extent of disease (EOD) grades in bone lesions and serum prostate specific antigen (PSA) levels according to treatment response.


Serial values of EOD grades and %PABS decreased during treatment in 11 patients with a partial response and in 12 with progressive disease who had no bone metastasis progression. However, EOD grades and %PABS increased in the remaining 19 patients with progressive disease who had bone metastatic progression. Estimated survival curves showed that %PABS was a useful prognostic indicator, in that patients with a > 25% decline in %PABS survived longer than those with a < 25% decline after treatment (P = 0.0207).


The %PABS is a simple and reproducible estimate of the proportion of the skeleton involving tumours in patients with advanced prostate cancer, and serial measurements of %PABS can assist in monitoring the treatment response in patients with bone metastatic prostate cancer.