Prognostic Value of Circulating Plasma Cells in Newly Diagnosed Multiple Myeloma

Multiple myeloma (MM) is biologically diverse and there is a significant variation in survival time from a few months to several years. The presence of circulating plasma cells (CPCs) is associated with a worse prognosis in patients with MM. This study retrospectively analyzed CPCs by 8-color multi-parameter flow cytometry in 108 cases of newly diagnosed MM patients to investigate its value for outcome prediction. Among them, 58 (53.7%) patients were CPCs positive expression. The optimum cutoff predicting for overall survival was determined as 0.29% by using a ROC analysis. Compared with patients with CPCs < 0.29% (n = 75, 69.4%), those with CPCs ≥0.29% (n = 33, 30.6%) showed lower Erythrocyte sedimentation rate(ESR) (P = 0.0032), but higher lactate dehydrogenase (LDH), ferritin (FER) , BM PCs and P53 deletion in BM by FISH (P = 0.001, 0.003, 0.014, and 0.001,respectively). With the median follow-up time 17 months (range, 2.0-37.0), the median PFS in the subgroups with CPCs<0.29% and ≥0.29% was not reached and17.0 months (95% confidence interval (CI):14.85-19.15), respectively, and the median OS was not reached and 12.5months (95% CI: 6.35-18.65), respectively. On multivariate analysis for OS, factors independently predictive of mortality were CPCs≥0.29% (hazard ratio (HR) 4.172; 95% CI, 1.61-10.79; P=0.003), Deletion P53(HR 11.54; 95% CI, 4.06-32.84; P<0.001). We further developed a convenient two-factor risk stratification based on CPCs and p53 deletion according to the results of log-rank test, univariate and multivariate analysis. The high-risk group was defined as both CPCs ≥ 0.29% and P53 deletion, accounting for 10% of the population, have a dire prognosis (median PFS = 5 months; OS = 10 months) despite modern therapies .These results identified CPCs as an unfavorable prediction for the outcome of MM. A combination of p53 deletion may screen out a high-risk subgroup which should be considered for novel therapeutic approaches.