ABSTRACT
BACKGROUND: Multiple myeloma (MM) immunophenotyping (IPT) and measurable residual disease (MRD) monitoring by flow cytometry is a surrogate for progression-free survival and overall survival in clinical trials. However, plasma cell enumeration is challenging owing to morphological discrepancies and plasma cell (PC) loss during the sample processing. METHODS: In (n=87) newly diagnosed MM patients, we evaluated the immunophenotype of PCs at baseline, and for a subset of 35 patients MRD at post-induction was quantified and analyzed for association with outcomes and survival. The software Statistical Package for Social Sciences (SPSS), version 16.0 (SPSS Inc., Chicago, IL, USA) was used for all the statistical analysis. RESULTS: Immunophenotyping showed strong positive expression of CD56 (83%), CD200 (94%), CD38 (92%), and CD117 (91%) and negative/weak expression of CD19 (83%), CD45 (89%), CD27 (74%), and CD81 (90%) respectively. Negative/weak expression of CD19 was significantly associated with age ≥56 years (p<0.048), with lower albumin (<3.4g/dL, p<0.001). Strong positive CD56 expression was significantly associated with the presence of M-protein (p<0.03). Strong positive CD117 expression was significantly associated with lower albumin (p<0.02). Strong positive CD200 expression was significantly associated with a good response (p<0.02). The median (IQR) value of bone marrow (BM)-MRD% was 0.005 (0.002-0.034). We found that there was no significant difference in the correlation, association, and survival outcomes with MRD%. CONCLUSION: This study sheds light on the utility of IPT as an invaluable diagnostic tool in disease management. The findings of this study could be important when it comes to modifying the criteria for high-risk diseases and implementing a risk-adapted first therapy in clinical practice.
ABSTRACT
BACKGROUND: Studies have shown that the quantification of circulating clonal plasma cells (cCPCs) in peripheral blood using flow cytometry could be used as a prognostic predictor of poor outcome in multiple myeloma (MM). METHODS: In 66 newly diagnosed MM, cCPCs were quantified (cCPC%) and analysed for association with outcome and survival. Single-tube combined surface (CD45/CD19/CD138/CD38/CD56/CD27/CD81 as per availability) and cytoplasmic (kappa/lambda) staining was done using pre-titrated volumes of antibodies. In 26 patients, repeat cCPC% was assessed post-induction therapy. For association studies, treatment response has been taken as good (VGPR and above) and poor (PR and below). All statistical analyses were performed with SPSS software version 16.0. RESULTS: There was no significant association between cCPC% at baseline with staging (p = 0.43), ß2 -microglobulin (p = 0.27) and albumin (p = 0.08). There was a significant difference between the pre-induction and post-induction cCPC% (p = 0.0001). The patients were segregated using a cut-off of ≥0.197 and <0.197 based on the median values of baseline cCPC%. The post-induction outcome was available for 47 patients among whom 33 (70%) had VGPR and above. There was a significant association between higher cCPC% at baseline with poor treatment response (p = 0.008). The median OS in the study patients was 42 (CI 28.14-43.03) months and the median PFS was 39 (CI 28.49-49.04) months. Higher cCPC% showed a lower median PFS (30 vs. 39 months) and OS (35 vs. 41 months) compared to lower cCPC% though it was not statistically significant. CONCLUSION: Flow cytometric baseline cCPC% in newly diagnosed MM was associated with poor treatment response and survival.
