Prognostic Implications of Measurable Residual Disease and Autologous Hematopoietic Stem Cell Transplantation in Primary Plasma Cell Leukemia in the Era of Novel Agents.

Primary plasma cell leukemia (pPCL) is the most aggressive malignancy of plasma cell disorders. While the clinical value of minimal residual disease (MRD) has been well established in multiple myeloma, there is a lack of data in patients with pPCL. Besides, the role of autologous hematopoietic stem cell transplantation (ASCT) needs to be reevaluated in the context of novel therapies. To evaluate the prognostic implications of MRD and ASCT in pPCL in the era of novel agents, in improving treatment response and outcomes in patients undergoing pPCL. We retrospectively conducted a single-center cohort study of all adult patients with newly diagnosed pPCL between 2017 and 2024. The status of MRD was assessed using next-generation flow cytometry on bone marrow aspirates with EuroFlow instrument settings. Statistical analyses were performed by R 4.4.1 and SPSS 26.0 software. A total of 70 newly diagnosed pPCL patients were included in the analysis, with a median overall survival (OS) and progression-free survival (PFS) of 33.5 months and 15.4 months, respectively. MRD-negative was identified as an independent prognostic factor for both OS (HR, 0.24; 95% CI, 0.06 to 0.98; P = .047) and PFS (HR, 0.29; 95% CI, 0.11 to 0.77; P = .013). These patients who achieved MRD negativity in first-line treatment demonstrated significantly longer median PFS (40.7 months) and not-reached OS. Additionally, following propensity score matching analysis, the 19 patients who underwent ASCT demonstrated a superior median OS (56.9 months versus 7.3 months, P < .001). Our study confirms the prognostic value of MRD negativity in pPCL for the first time. Our findings also support that ASCT can potentially provide response and survival benefits in the era of novel agents.