Prognostic value of circulating clonal plasma cells in newly diagnosed multiple myeloma.

OBJECTIVES Multiple myeloma (MM) involves a clinically and biologically heterogeneous malignancy of plasma cells. It is difficult to predict the prognosis of MM. The presence of circulating clonal plasma cells (CPC) has been associated with a worse prognosis in patients with MM. METHODS This study retrospectively analysed CPC in 108 newly diagnosed MM patients by 8-colour flow cytometry to investigate their value for predicting the outcome and combined the level of CPC with the revised International Staging System (R-ISS) to stratify the MM patients according to risk. RESULTS CPC were detected in 58/108 patients (53.7%). The optimum cut-off for the prediction of overall survival was determined to be 0.105%. Patients with higher R-ISS stages seemed to harbour more CPC. A level of CPC≥0.105% was an independent risk factor for adverse outcomes (P<0.001). The combination of the R-ISS staging system and level of CPC was used to stratify MM patients according to risk, and the combination of R-ISS stage III and a level of CPC≥0.105% defined the ultra-high-risk group. CONCLUSION This study suggests that a high proportion of CPC is associated with aggressive disease and that the use of the current R-ISS system in conjunction with assessment of the level of CPC may facilitate the stratification of newly diagnosed MM patients into clinically relevant prognostic subgroups.