Validation of a Sensitive Flow Cytometry Assay to Assess Minimal Residual Disease of Multiple Myeloma Cells in Apheresis Product

For treatment of patients with multiple myeloma (MM), flow cytometry has become a widely used and valuable method for the evaluation of minimal residual disease (MRD) in bone marrow. Use of an optimized single-tube, 10-color flow cytometry panel for assessment of MM MRD has shown to be beneficial in patient monitoring and has shown correlation to the acknowledged EuroFlow 8-color, 2-tube method. In order to further correlate levels of MM and relapse in patients, validation of a sensitive MM MRD assay that can be applied to testing for residual disease in apheresis product prior to autologous stem cell transplant, a standard treatment for patients with multiple myeloma. This approach can exhibit great value in patient monitoring and treatment. As new combination therapies are developed for treatment of multiple myeloma in concert with autologous stem cell transplantation, evaluation of MRD in apheresis will likely continue to grow in importance. The purpose of this study is to show the validation and sensitivity of a flow cytometry assay designed to detect Multiple Myeloma (MM) cells in G-CSF and other mobilized apheresis samples from human Multiple Myeloma patients. Using GSM-mobilized apheresis product, spiked with different levels of patient de-identified MM plasma cells, validation of a 10-color MM MRD panel can be evaluated, intended to mimic patient apheresis at varying levels of residual disease post treatment. As with any minimal residual disease assessment, a high number of events are required to ensure sensitivity and precision. Typically, acquisition of 3-5 x 10⁷ events is required to ensure precision of MM MRD levels to 0.001%.