# Outcomes of pPCL Diagnosed Using the IMWG 2021 Consensus Definition: A Retrospective Multicenter Analysis

## TL;DR

This study examines outcomes of primary plasma cell leukemia patients using updated diagnostic criteria and finds that stem cell transplants remain effective despite aggressive disease.

## Contribution

The study provides one of the largest cohorts using the 2021 IMWG pPCL criteria and evaluates treatment outcomes with novel therapies.

## Key findings

- Autologous stem cell transplant improves overall response rate and progression-free survival in pPCL patients.
- High-risk cytogenetics is an independent risk factor for disease progression in pPCL.
- Fewer pPCL patients undergo transplants compared to less aggressive plasma cell disorders.

## Abstract

Primary plasma cell leukemia (pPCL) is an aggressive plasma cell dyscrasia with an extremely poor prognosis. Recently, the definition of pPCL was broadened to include patients with fewer circulating plasma cells at diagnosis. We retrospectively examined outcomes in patients diagnosed with pPCL treated with novel therapies using the updated diagnostic criteria. Our data suggests that autologous stem cell transplant remains an effective treatment for these patients even after treatment with induction regimens containing novel therapies. However, our data also shows that a smaller proportion of pPCL patients undergo transplant compared to patients diagnosed with less aggressive plasma cell dyscrasias, most likely due to the aggressive nature of the disease. Our study underscores the need for rapid diagnosis and treatment in pPCL in hopes of preserving a patient’s transplant eligibility.

Background: Primary plasma cell leukemia (pPCL) represents the most aggressive plasma cell dyscrasia with a poor prognosis and survival of <3 years. The International Myeloma Working Group (IMWG) adopted more inclusive diagnostic criteria for pPCL in 2021, including patients with 5% or more circulating plasma cells (down from 20%). Most published studies of pPCL do not include patients who meet the criteria for pPCL based on the newer diagnostic guidelines, and the data on the optimal treatment of pPCL is scarce. In our multi-center retrospective analysis, we report data on treatment regimens used in 67 pPCL patients to characterize outcomes in this population. Methods: We included patients with newly diagnosed pPCL between 2010 and 2023 based on the 2021 IMWG definition at one of three academic centers. Results: Our results suggest significant improvement in overall response rate (ORR) and progression-free survival (PFS) with the use of autologous stem cell transplant, but without additional benefit for a tandem transplant. The presence of high-risk cytogenetics was an independent risk factor for progression in the cohort. Conclusions: Our dataset represents one of the largest cohorts to date using the expanded definition of pPCL adopted by the IMWG in 2021 and stresses the importance of taking pPCL patients to transplant. Unfortunately, our study was not powered to determine the efficacy of individual induction and maintenance regimens, and many patients diagnosed with pPCL are ineligible for transplant based on end-organ damage at diagnosis or from disease that is refractory to induction therapy, underscoring the need for early diagnosis and treatment in hopes of preserving transplant eligibility.