MM-252: Aberrant Plasma Cells in the Apheresis Product as a Prognostic Factor for Minimal Residual Disease Negativity After Transplant in Newly Diagnosed Myeloma Patients

Abstract

Context: Autologous stem cell transplantation (ASCT) is the standard frontline therapy for newly diagnosed multiple myeloma (MM) eligible patients. “Contamination” of leukapheresis products with aberrant plasma cells (PCs) has been considered as a possible predictive factor for response and outcome. Objective: To evaluate the frequency and clinical value of clonal PCs remaining in leukapheresis products using next generation flow cytometry (NGFC), which is able to detect aberrant clonal PCs at levels reaching 10−6. Design: Prospective study. Setting: A referral center in Athens, Greece. Patients: MM patients after four cycles of induction therapy (VCD or VRD) followed by ASCT in the Department of Clinical Therapeutics, University of Athens, Greece. Interventions: Ninety-eight patients with newly diagnosed multiple myeloma were assessed for the presence of clonal PCs with the 8-color NGFC protocol suggested by EuroFlow. Eight to ten million cells were examined; the median sensitivity of the test was 2–4 × 10−6 per sample. All patients received high-dose melphalan and ASCT. Using the same NGFC protocol, 53 patients who achieved complete response (CR) post-ASCT, based on the IMWG criteria, were also examined for the presence of minimal residual disease (MRD). Main outcome measures: Aberrant PCs in leukapheresis products. Results: This analysis revealed 58 (59%) “uncontaminated” (con-) and 40 (41%) “contaminated” (con+) leukapheresis products. The majority of con+ cases had very low numbers of aberrant plasma cells detected; 18 (45%) at the level of 10−615 (38%) at the level of 10−4 and 7 (18%) at levels ≥10−3. On day 100 post-ASCT, MRD evaluation was performed on 33 con- and 20 con+ patients, who had achieved CR. MRD positivity was found in 11 out of 53 cases (20.8%). Only 3 out of 33 (9.1%) con- patients were found MRD+, all of which at very low levels ( Conclusions: Using NGFC, we were able to detect aberrant plasma cells in 40% of apheresis products at the level of 10−6. The presence of aberrant plasma cells in the apheresis products correlates with higher probability for MRD+ after ASCT, whereas their absence predicts MRD negativity.