Survival Outcomes of Patients with Primary Plasma Cell Leukemia in the Era of Proteasome Inhibitors and Immunomodulatory Agents: A Real-Life Multicenter Analysis

Objective: In this study, we aimed to obtain real-life data on the use of antimyeloma agents, which significantly increase overall survival (OS) in multiple myeloma (MM) patients, in primary plasma cell leukemia (pPCL) patients with poor prognosis. Materials and Methods: Data from 53 patients who were diagnosed with pPCL between 2011 and 2020 and who used at least one proteasome inhibitor (PI) and/or immunomodulatory (IMID) agent were analyzed retrospectively. Depending on the year of the pPCL diagnosis, 20% leukocytes or ≥2x109/L plasma cells in the peripheral blood was used as a diagnostic criterion. Results: The median age of the patients was 58 years and 23 (43.4%) patients were over 65 years of age. For first-line treatment, PI or IMID alone was used by 31 (58.5%) patients, and PI and IMID were used simultaneously by 15 (28.3%) patients. Additionally, 21 (39.6%) patients received transplantation and 13 (24.5%) patients received maintenance treatment. The median progression-free survival was 4 (range: 1-42) months. When patients whose primary disease was refractory to first-line therapy were excluded, the duration of treatment was 6.5 months. The median OS was 15 months with a median follow-up duration of 15 months. Only 7 (13.2%) of the patients were alive at the last follow-up visit. Those with higher β2-microglobulin levels and International Staging System stage 3 and non-transplant patients receiving first-line treatment had shorter OS (p=0.005, p=0.02, and p=0.008, respectively). The concomitant use of PIs and IMIDs, the addition of chemotherapy to induction therapy, and the response to induction therapy or maintenance therapy did not affect OS. Conclusion: In this study, as in previous similar studies, we could not see an increased survival trend in pPCL, which is observed in MM. New studies are needed for pPCL, which is likely to increase with new diagnostic criteria, based on current agents and information from MM.