ABSTRACT
Objective: To analyze the efficacy and safety of first-line treatment with an anti-CD38 monoclonal antibody regimen for primary plasma cell leukemia (pPCL). Methods: Patients diagnosed with pPCL from December 1st, 2018 to July 26th, 2023, receiving first-line treatment of anti-CD38 monoclonal antibody-based regimens across multiple centers including Peking University People's Hospital, Fuxing Hospital of Capital Medical University, Qingdao Municipal Hospital, Shengjing Hospital of China Medical University, Handan Central Hospital, the First Affiliated Hospital of Harbin Medical University, the Fourth Hospital of Hebei Medical University and General Hospital of Ningxia Medical University were consecutively included. A total of 24 pPCL patients were included with thirteen being male and eleven being female. The median age [M(Q1, Q3)] was 60 (57, 70) years. Patients were grouped according to peripheral blood plasma cell (PBPC) percentage [5%-19% (n=14) vs ≥20% (n=10)]. Last follow-up date was September 26th, 2023. The median follow-up period was 9.1 (4.2, 15.5) months. Patients' data related with clinical baseline characteristics, efficacy, survival and safety were retrospectively collected. Cox proportional hazards regression model was used to analyze risk factors associated with survival. Results: Among 24 pPCL patients, 16 (66.7%) patients had anemia at diagnosis, 13(54.2%) patients had thrombocytopenia, 8 (33.3%) patients had a baseline estimated glomerular filtration rate (eGFR)<40 ml·min-1·(1.73m2)-1, 13 (54.2%) patients had elevated lactate dehydrogenase (LDH) levels. The median PBPC percentage was 16% (8%, 26%) . Fluorescence in situ hybridization testing indicated that patients harboring 17p deletion, t(4;14) or t(14;16) were 6 (25.0%), 4 (16.7%) and 4 (16.7%), respectively. The overall response rate was 83.3% (20/24). The median progression-free survival (PFS) was 20.5 (95%CI: 15.8-25.2) months, and the median overall survival (OS) was not reached. Estimated 1-year and 2-year PFS and OS rates were 75.0% and 89.1%, 37.5% and 53.4%, respectively. The median PFS and OS for patients with PBPC percentages 5%-19% and≥20% were not reached and 20.5 (95%CI:15.7-25.3) months, 17.8 months and not reached, respectively. There was no significant statistical difference of PFS and OS between two groups (all P>0.05). Multivariate Cox regression analysis showed that 1p32 deletion was the risk factor associated with PFS (HR=7.7, 95%CI: 1.1-54.9, P=0.043). Seventeen patients (70.8%) developed grade 3-4 hematologic toxicities. Twelve patients (50.0%) developed grade 3-4 thrombocytopenia. Sixteen patients (66.7%) developed infection. All hematologic toxicities and infections were improved after supportive treatment. Conclusion: First-line treatment with anti-CD38 monoclonal antibody-based therapy for pPCL is effective and safe.