P-431: Clinical characteristics, prognostic factors and treatment outcomes in patients diagnosed with primary plasma cell leukemia based on the revised criteria (KMM2204)

Introduction: Recently, the diagnostic criteria for plasma cell leukemia (PCL) were revised to lower the cut-off value of 5% circulating plasma cells (CPCs) in peripheral blood smear.

Methods: This retrospective study evaluated the clinical characteristics, prognostic factors and treatment outcomes in patients diagnosed with primary PCL based on the revised criteria.

Results: At diagnosis, 127 patients diagnosed with primary PCL; 70 had CPCs ≥ 20%, and 57 had CPCs 5-19%. The study found no significant difference in progression free survival (PFS) and overall survival (OS) between the two groups (CPCs≥ 20% and 5-19%), but patients with CPCs≥20% had significantly higher white blood cell counts, lactate dehydrogenase levels and extramedually plasmacytoma compared to those with CPCs 5-19%. Multivariate analysis identified poor performance status, thrombocytopenia and del17p as significant predictor of OS. In this study, 33 patients underwent 18F-FDG PET/CT prior to initial treatments, and 11 showed more than 3 focal lesions. However, there was no difference of survival outcomes according to the PET/CT postivity. In addition, patients who achieved a complete response (CR) after induction therapy showed significantly improved PFS and OS than other patients. When evaluating response rates according to the induction therapies such as daratumumab-based quadruplets, bortezomib and thalidomide or bortezomib and lenalidomide combinations, bortezomib-based combinations, and IMiDs based combinations, CR rate was the highest in daratumumab-based quadruplets than other induction therapy.

Conclusions: In conclusion, while there were some clinical and laboratory differences bwteeen patients with CPCs 5-19% and ≥ 20%, there was no difference in survival outcomes. Achieving CR after induction therapy was crucial for improving survival outcomes, and daratumumab-based quadruplets may be reasonable choice as an induction therapy for primary PCL.