Predictors of bone metastasis in pre-treatment staging of asymptomatic treatment-naïve patients with prostate cancer.

BACKGROUND There is no general consensus on the optimal criteria for the application of bone scintigraphy in screening of bone metastasis in patients with prostate cancer. Our study was conducted to assess the value of bone scan for pre-treatment staging of asymptomatic treatment-naïve patients with prostate cancer. METHODS A total of 203 consecutive asymptomatic and treatment-naïve patients with prostate cancer (age: 67.6±6.4 years) who were referred to our department for whole body bone scintigraphy were enrolled in the study. Three hours after intravenous injection of 20mCi (99m)Tc-MDP, all patients underwent whole body bone scanning using a single head gamma camera. The planar images were supplemented with SPECT as needed for questionable abnormalities or those having uncertain location on planar images. RESULTS The mean serum PSA levels, serum alkaline phosphatase (ALP) and Gleason score (GS) were 42.41±37.1ng/ml, 223.9±129.9IU/L and 6.7±1.1, respectively. A total of 55 cases (27.1%) out of 203 patients had bone metastases. The univariate analysis showed that serum PSA levels, GS and ALP were all significant predictors of bone metastases. However, only serum PSA and ALP levels were found to be independent predictors of bone metastasis in the multivariate logistic regression analysis. The combination of PSA and ALP (in which patients with either elevated PSA [>20ng/ml] or elevated ALP were considered as positive) had the best screening value, with 98.2% sensitivity and 48.6% specificity. CONCLUSION Serum ALP screening can be employed as a tool to detect the subgroup of patients who are at high risk of bone metastases, while having a PSA of <20ng/ml. The combination of PSA and ALP can be used to improve predictability of bone metastasis in newly diagnosed patients with prostate cancer, without affecting staging accuracy.