Introduction: Plasma cell leukemia (PCL) is a rare and aggressive plasma cell disorder with poor prognosis. The median survival of plasma cell leukemia is in months with slightly improved survival in patients who undergo hematopoietic stem cell transplantation (HSCT). Multi-agent cytotoxic chemotherapy is generally recommended but carries significant toxicity. Novel agents have shown promise, but there is limited data. PCL may present de novo (primary) or evolve from multiple myeloma (secondary). This single-institution study evaluates treatment outcomes and survival among patients diagnosed with PCL.
Methods: We conducted a retrospective review of all patients diagnosed with PCL from Jan 1st, 2017 to Jan 1st, 2025. High risk cytogenetics were defined as t(4;14), t(14;16), t(14;20), del(17p), 1q gain and hypodiploidy. We analyzed response rates, HSCT status, overall survival (OS) and progression free survival (PFS). Time-dependent Cox regression analysis was conducted to examine the hazard ratio between the two groups, based on HSCT status. Statistical significance was set at p< 0.05 using SAS 9.4.
Results: Our sample size included 28 patients who had a diagnosis of PCL. We found that amongst those who did not undergo HSCT, the mean age was 70 years, 50% patients had high-risk cytogenetics, 56.25% patients had primary PCL and 62.5% patients were treated with novel agents. However, amongst patients who underwent HSCT, the mean age was 65 years, 50% patients had high-risk cytogenetics, 58.3% patients had primary PCL, and 91.6% of patients were treated with novel agents for induction prior to the HSCT. Amongst patients who had HSCT, 16.7% patients had complete remission (CR), 50% had very good partial response (VGPR), 33.3% patients had partial response (PR), and no one had progressive disease, prior to the transplant. This was significantly different (p=0.0002) from patients who did not undergo HSCT, with 12.5% patients having CR, 6.25% patients with PR, 6.25% patients with VGPR, and 12.5% patients with progressive disease. And response could not be assessed in 62.5% of patients. Given sample size and method of analysis there was no statistically significant difference in OS and PFS between HSCT and Non-HSCT cohorts. However, 33.33% of patients remained in remission after getting HSCT as opposed to 0% patients in the non-HSCT cohort (p-value < 0.001).
Conclusions: In our single institution study, plasma cell leukemia continues to exhibit poor outcomes. However, the use of novel agents was linked to improved response rates and increased eligibility for HSCT. The small sample size remains a key limitation of our study and larger multi-institutional studies are needed to establish optimal treatment strategies.
