Serum bone sialoprotein as a marker of tumour burden and neoplastic bone involvement and as a prognostic factor in multiple myeloma

To test the potential of immunoreactive BSP, a non-collagenous bone matrix component, as a clinical guide in patients with plasma cell dyscrasias, ser um BSP concentrations were measured in 62 patients with newly diagnosed mul tiple myeloma (MM) followed over a period of 4 years, in 46 patients with m onoclonal gammopathy of undetermined significance (MGUS), in 71 patients wi th untreated benign vertebral osteoporosis (OPO), and in 139 healthy adults . Results were compared with clinical and laboratory data, including serum osteocalcin (OC), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD ) as markers of bone turnover. In MM, serum BSP, and urinary PYD and DPD we re higher than in healthy controls and in MGUS or OPO (P< 0.001). BSP level s correlated with the bone marrow plasma cell content (r = 0.40, P < 0.001) , and serum beta (2)-microglobulin (r = 0.31, P < 0.01). The differentiatio n of MM from healthy controls and from MGUS or OPO was highest for BSP. Aft er chemotherapy, BSP reflected the response to treatment and correlated wit h the change in monoclonal protein (r = 0.55, P< 0.001). MM patients with n ormal baseline BSP levels survived longer than patients with initially elev ated BSP values (P < 0.001, logrank test). Only serum monoclonal protein an d BSP were independent predictors of survival. We conclude that in MM, BSP levels are associated with skeletal involvement and tumour cell burden. The quantification of serum BSP may be a non-invasive method for the diagnosis and follow-up, and may improve the prognostic value of conventional stagin g in MM. (C) 2001 Cancer Research Campaign.