Prognostic significance of alkaline and acid phosphatase and skeletal scintigraphy in carcinoma of the prostate.

The prognostic significance of skeletal scintigraphy has been reassessed in relation to other tests by extended follow-up of 220 patients. Skeletal metastases increased in prevalence with T stage and were associated with shorter survival irrespective of age. Early disease, a normal acid or alkaline phosphatase at presentation and well differentiated tumours were associated with longer survival. Alkaline phosphatase alone accounted for all of the differences in survival. Scintigraphic change preceded elevation of the prostatic acid phosphatase in 81% of the patients whose initial scintigraphy and prostatic acid phosphatase were normal but who developed evidence of distant metastases on follow-up. The mean interval between scintigraphic conversion and the development of overt symptoms was 5.8 months. Our findings discount the value of skeletal scintigraphy for determining prognosis but do indicate that it is more sensitive than the acid phosphatase in identifying patients before they become symptomatic. Scintigraphy is indicated as a routine staging procedure in all new patients with carcinoma of prostate. In patients with a normal alkaline phosphatase, a baseline and regular follow-up are needed to identify patients likely soon to develop symptoms. If the alkaline phosphatase is elevated at presentation, scintigraphy is necessary to distinguish benign from malignant causes and to determine the extent of skeletal involvement.