Value of prostate specific antigen in predicting the existence of bone metastasis in scintigraphy

ABSTRACT

OBJECTIVE: Evaluate the ability of serum concentration of prostate specific antigen (PSA) between 2 cutting points to predict the existence of bone metastasis confirmed by bone scintigraphy in man with prostate cancer. MATERIALS AND METHODS: Two hundred and fourteen consecutive patients with prostate cancer were evaluated during the present study in the period from 1998 to 2001. From all patients, PSA serum concentrations and bone scintigraphy were obtained. For the study, 2 cutting points of PSA (10 and 20 ng/mL) were adopted to predict the existence of bone metastasis. RESULTS: From the 214 patients, 35 (16.3 percent) presented positive scintigraphic examinations for the presence of bone metastasis. No patient presented bone metastasis in scintigraphy if having PSA < 10 ng/mL, and in only 1 patient (0.46 percent) with bone metastasis PSA concentration was < 20 ng/mL. Therefore, when the cutting point adopted for PSA serum concentration was 10 ng/mL, a negative predictive value for bone metastasis was 100 percent with sensitivity rates of 100 percent. Nevertheless, the positive predictive value and the specificity of the method were, respectively, 24.5 percent and 39.7 percent. When the cutting point of PSA serum concentration was 20 ng/mL, an increment was observed in rates of positive predictive value and specificity (41.5 percent and 73.2 percent), respectively, without substantial changes in negative predictive value (99.2 percent) and sensitivity (97.1 percent) of the method. CONCLUSIONS: Data of present study allow for the conclusion that PSA serum concentration over 20 ng/mL was a more accurate cutting point than PSA serum concentration over 10 ng/mL to predict the presence of bone metastasis in scintigraphy