Serum ProGRP as a novel biomarker of bone metastasis in prostate cancer.

•Serum ProGRP level was higher in PCa patients with bone metastasis versus non-bone metastasis.•Serum ProGRP level was correlated with the presence of bone metastasis in prostate cancer.•Serum ProGRP level could distinguish bone metastasis from non-bone metastasis in PCa.•The combination of ProGRP, F-PSA and T-PSA was better than any biomarker alone.