BACKGROUND The alteration of the bone microenvironment as a consequence of skeletal metastases is poorly understood. The aim of this study was to search for patterns of bone markers in relation to primary tumor type, bone pain, and number of sites involved in patients with bone metastases. METHODS We studied 323 patients with bone metastases from various primary malignancies. We sequentially measured the serum concentrations of bone alkaline phosphatase [by an electrophoretic technique (BALP)], carboxy-terminal telopeptide of type I collagen (ICTP), calcium (CaS), intact parathyroid hormone (PTH), and the fasting urinary excretion of calcium (Ca:Cr). Immunoradiometric serum bone alkaline phosphatase (I-BALP) and urinary excretion of deoxypyridinoline (DPYD) were also assessed in the 175 cases. Data were analyzed as a function of bone pain (assessed by a validated pain questionnaire), the number of radiographically confirmed sites of bone involvement, and the most frequent primary tumor types: breast cancer (BC; 124 patients), prostate cancer (PC; 90 patients), and non-small cell lung cancer (LC; 49 patients). RESULTS Serum BALP and I-BALP correlated with the number of radiologically identified blastic bone lesions. BALP and I-BALP were more frequently increased in PC (72% for both measurements) than in BC (50% and 60%, respectively) or LC (3% and 5%, respectively; P <0.001 for BALP and P = 0.001 for I-BALP). ICTP and DPYD values did not differ among PC, BC, and LC, but they did show a direct relationship with the disease extent in bone (P <0. 001). CaS and Ca:Cr did not vary significantly according to the bone tumor burden. Bone pain directly correlated with ICTP (P <0.001), DPYD (P = 0.002), CaS (P <0.002), and Ca:Cr (P = 0.001), whereas the relationship was inverse for serum PTH (P = 0.002). When patients were stratified according to the primary tumor, ICTP correlated with the bone pain in all subsets (P <0.005, <0.005, and <0.001 for BC, PC, and LC, respectively), as did CaS and Ca:Cr in LC patients (P = 0.01 and 0.02, respectively) but not in PC and BC patients. CONCLUSIONS The patterns of bone turnover markers differ among the primary tumor types. Both resorption and formation markers reflect the number of radiographically identified sites of bone metastases, whereas resorption markers and serum calcium but not formation markers correlate with bone pain.