When is bone scintigraphy necessary in the assessment of newly diagnosed, untreated prostate cancer?

To evaluate the utility of bone scintigraphy in the assessment of newly diagnosed, untreated prostate cancer.

The probability of a positive bone scan for metastases was analysed for different threshold values of pre-treatment concentrations of prostate specific antigen (PSA), clinical stage, tumour grade based on biopsy, and age in 128 men (mean age 69 years, range 50-90) with newly diagnosed, untreated prostate cancer. The overall survival probabilities estimated from PSA level, extent of bone metastases, tumour grade, clinical stage, and age were calculated using the product-limit method.

The positive predictive values of PSA level for bone metastases at thresholds of 10 and 20 ng/mL were poor (27.5 and 47.5%, respectively) whereas similar threshold levels of PSA gave negative predictive values of 100 and 94%, respectively, for a positive bone scan. In a univariate analysis, the overall survival was significantly affected by the extent of bone scan pathology (P < 0.001), the pre-treatment level of PSA (P < 0.001) and tumour grade (P = 0.01), whereas a multivariate analysis identified, in order of significance, tumour grade (P = 0.003), bone scan findings (P = 0.007) and PSA levels (P = 0.03) as independent prognostic factors.

Bone scintigraphy seems to be unnecessary in the evaluation of newly diagnosed, untreated prostate cancer in patients with no clinical signs of bone pathology and serum PSA levels of < or = 10 ng/mL. However, the bone scan accurately assesses bone metastases and the prognostic significance of bone scan findings is superior to that of serum PSA level.