Alternative methods include bone biopsy [203] and identification of blood markers such as alkaline phosphatase [204,205] and calcium [206], which together with age-specific reference ranges, metastasis indicators, hemoglobin, Gleason score, treatment conditions, prostate-specific antigen (PSA), bone-specific alkaline phosphatase, corrected urinary N-telopeptide (uNTx), and absence of visceral metastasis, constitute the prognostic factors of PCa bone metastasis [207,208,209,210]. Here, KLK3 is linked to bone metastasis.