Objective: To explore the significance of serum bone metabolic markers in the diagnosis and monitoring of multiple myeloma bone disease(MBD).
Methods: Thirty-six newly diagnosed multiple myeloma (MM) patients who were treated in Department of Hematology, Tianjin Medical University General Hospital from January 2013 to December 2014 were collected. Bone morbidity was graded into two stages according to the radiographic evaluation of the skeleton: stage A (n=12) included patients with no lytic lesions or with osteoporosis alone; stage B (n=24) included patients with osteolytic lesions and/or a pathological fracture. All the patients achieved partial or complete remission after treated with bortezomib + dexamethasone + zoledronic acid regimen. A total of 25 aged- and gender-matched healthy individuals were enrolled in this study as controls. The levels of serum tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), carboxy-terminal cross-linking telopeptide of type I collagen (CTX), osteocalcin (OCN), and procollagen I amino-terminal propeptide (PINP) were investigated by ELISA and electrochemiluminescence immunoassay (ECLIA). The differences of these bone metabolic markers before and after treatment, and at different stages of bone disease were observed.
Results: The value of TRACP-5b in the newly diagnosed MM was significantly higher than that in the healthy controls and after treatment(median 4.16 vs 2.63 U/L, P=0.014; 4.16 vs 2.61 U/L, P=0.037). Serum level of CTX in the newly diagnosed MM patients was significantly decreased after treatment (median: 0.26 vs 1.05 µg/L, P=0.003). The ratio of CTX/OCN and CTX/PINP decreased after treatment, but there were no significant differences (both P>0.05). The pretreatment level of serum TRACP-5b in stage B patients was higher than that of the healthy controls (median: 4.20 vs 2.63 U/L, P=0.015). The levels of serum CTX in stage A and stage B patients were both higher than that of the healthy controls (median: 1.16 vs 0.48 µg/L, P=0.002; 0.88 vs 0.48 µg/L, P=0.040). The levels of serum OCN and PINP were higher in stage A patients compared with stage B patients, but there were no significant differences (both P>0.05). The ratio of CTX/OCN and CTX/PINP of stage A and stage B patients all increased compared with those of the healthy controls, but there were no significant differences (all P>0.05).
Conclusions: Bone damage of MM patients is improved after effective treatment, but bone imbalance still exists, indicating that the treatment of MBD is a long process. Abnormal serum levels of TRACP-5b and CTX are found before positive X-ray findings in MBD, suggesting that these biochemical markers could be used as indices for early diagnosis of MBD.