Soluble syndecan-1 at diagnosis and during follow up of multiple myeloma: a single institution study

BACKGROUND: Syndecan-1 is a heparan sulfate proteoglycan expressed on plasma cells, especially myeloma cells, and can exist in serum as soluble syndecan-1 after shedding from the cell surface. Soluble syndecan-1 has been suggested to promote myeloma cell growth and to be an independent prognostic factor for multiple myeloma. We aimed to evaluate the effect of soluble syndecan-1 levels at the time of diagnosis and during therapy on therapeutic response and prognosis for patients with multiple myeloma. METHODS: We analyzed soluble syndecan-1 levels in 28 patients with multiple myeloma and 50 normal controls, and compared its levels with Durie-Salmon stage and other markers of myeloma. In addition, we evaluated the therapeutic response and determined the 3-year survival rates of these patients. RESULTS: We observed that the median soluble syndecan-1 level in myeloma patients was higher than that in the normal controls (P <0.0001), and the soluble syndecan-1 levels in 21 (75%) patients were higher than the cut-off level (162 ng/mL). Soluble syndecan-1 levels correlated with disease stage, percentage of plasma cells in the bone marrow, β(2) microglobulin level, serum M-component concentration, and creatinine level. The baseline levels of soluble syndecan-1 at the time of diagnosis in the patients who responded to chemotherapy were lower than those in the non-responders (P=0.04); however, the baseline level was not a significant predictor of therapeutic response. The 3-year overall survival rate of the patients with high soluble syndecan-1 levels at the time of diagnosis and 6 months after chemotherapy was lower than the corresponding survival rates of the patients with low levels of soluble syndecan-1; however, the overall survival rate was not statistically significant. CONCLUSION: The use of soluble syndecan-1 has limitations in the diagnosis of multiple myeloma. Soluble syndecan-1 levels correlate with known prognostic factors; however, we could not assess the prognostic value of high levels of soluble syndecan-1 at the time of diagnosis and after chemotherapy.