DP117 | THE TREATMENT OF TRANSPLANT ELIGIBLE PRIMARY PLASMA CELL LEUKEMIA PATIENTS: AN ITALIAN REAL-LIFE STUDY

Primary plasma cell leukemia (pPCL) is a rare variant of plasma cell malignancy characterized by at least 5% circulating plasma cell (cPC), aggressive behavior and ominous prognosis. Though to the rarity of the disease, the choice of treatment is most based on real world evidence and expert consensus. Moreover, the roles of daratumumab (Dara) and chemotherapy-based (Chemo) combinations in the induction therapy is not well established. The aim of this study is to retrospectively and prospectively evaluate in real-life the first-line treatment and the outcome of transplant eligible (TE) pPCL patients. From 2009 to 2025 we collected 143 pPCL patients (54 with 5-19% cPC and 89 with > or=20% cPC) followed in 27 Italian Centers. Median age was 60 years (28-77). The cohort was enriched in high-risk disease features, including R2-ISS IV in 42.9% of cases (42/98) high LDH levels in 56.2% (77/136) of cases and extramedullary disease in 20.5% (28/137) of cases. Finally, 57.7% (64/111) of patients showed high-risk cytogenetic. Considering the induction, 60/143 (42%) patients received a Dara-based induction and 59/143 (41.3%) patients a combination of Chemo+/-PI+/-IMIDS+/-Dara induction, respectively. Only 51.1% of cases (73/143) achieved at least a stem cell transplantation (SCT) in first line, with 30/73 (41.1%) receiving a single AutoSCT, 33/73 (45.2%) tandem AutoSCT and 10/73 (13.7%) AlloSCT. Moreover, after SCT, 28/64 (43.8%) patients started maintenance. With a median follow-up of 15 months, the median PFS and OS were 18 months and 31 months, respectively. An increased PFS, was demonstrated in patients treated with Dara-based regimen (36 vs 16 months, p=0.1337) or Chemo-based regimen (29 vs 15 months, p=0.1246). Of notice, patients receiving tandem AutoSCT or AlloSCT showed higher PFS and OS compared to those who received single AutoSCT (tandem AutoSCT vs single AutoSCT: PFS=38 vs 15 months, p=0.0011; OS=72 vs 23 months, p<0.0001; AlloSCT vs single AutoSCT: PFS=98 vs 15 months, p=0.0121; OS=102 vs 23 months, p=0.0136). Finally, patients who received maintenance displayed a significant improvement in PFS (45 vs 18 months, p=0.0019) and OS (not reached vs 29 months, p=0.0042) with respect to observation. Herein we reported one of the largest cohorts of TE pPCL patients. The preliminary data presented showed promising efficacy for Dara or Chemo in induction treatment and, most importantly, for tandem AutoSCT or AlloSCT and maintenance therapy in the first line treatment.