Detection of minimal residual disease after induction chemotherapy and autologous HSCT and its clinical significance in multiple myeloma

Background. Minimal residual disease (MRD) study is a necessary step for detailed analysis of tumor clone persistence in bone marrow of patients with multiple myeloma (MM), which is important for assessing the depth of remission during treatment. MRD assessment can be useful for building a prognosis of MM and choosing patient management tactics. Aim. To assess the frequency of MRD and its prognostic significance in patients with MM during treatment. Materials and methods. The study included 56 patients with MM, the average age of which was 54.9 ± 1.3 years. All patients received induction chemotherapy, which was carried out according to the Vrd regimen. After induction therapy and 100 days after autologous hematopoietic stem cell transplantation (auto-HSCT), MRD status was assessed. MRD status was assessed by multicolor flow cytometry (FACSCanto II, Kaluza Analysis v2.1 software, USA). Monoclonal antibodies: CD45, CD19, CD27, CD56, CD28, CD38, CD117, CD19, CD81, immunoglobulin light chains kapa / lambda, 7ADD (Becton Diсkinson, USA). Results. The frequency of MRD-negative status after induction therapy was 35.7 %, after auto-HSCT – 56.7 %. A decrease in the number of abnormal plasma cells (PC) in the bone marrow by 1.3 times was noted compared to the induction therapy stage. Conversion of MRD-positive cases was established during treatment. In the group with the PC content in the bone marrow after induction therapy more than 0.01 %, but less than 0.1 %, the MRD status changed after auto-HSCT and became negative in 53 % of patients. In the presence of PC more than 0.01 % after induction, the progression rate increased more than 2-fold and was 50.0 % ( p <0.05). The average number of PCs in patients without disease progression detected after auto-HSCT was significantly lower: 0.02 % versus 0.31 %, p <0.05. Conclusion. The frequency of MRD-negative status at the stage of induction therapy and after auto-HSCT differs, so several control points are important. After auto-HSCT, there is a conversion of MRD-positive cases to negative ones. Progression of MM was observed more often with MRD-positive status. Monitoring of MRD can help in selecting candidates for joining maintenance treatment of MM.