Survival outcomes in patients with primary plasma cell leukemia treated with novel therapies at University of California San Diego Health: A single institution experience.

Abstract

e19538 Background: Plasma Cell Leukemia (PCL) is a rare, but aggressive and devastating disease for which there is a paucity of data regarding the efficacy and safety of modern therapies to guide management. Data prior to the use of modern therapies showed abysmal overall survival (OS) of approximately 4-12 months. There is generally agreement that novel therapies have improved outcomes, but data supporting this is sparse due to the rarity of the disease. As such, there is currently no standard of care agreed upon by experts, and the specific approach for treatment currently varies by provider. Methods: In this single-center retrospective study, we review the outcomes of patients diagnosed with primary plasma cell leukemia (pPCL) from 2008 to 2023 who received at least one of the novel therapies of immunomodulatory drugs (IMiD), protease inhibitors (PI), and/or anti-CD38 antibodies at University of California San Diego Health. Baseline characteristics and efficacy outcomes were collected. Results: A total of 11 patients were identified who met the inclusion criteria. The median age at time of diagnosis was 50. The median circulating plasma cells at diagnosis was 34%. All but 2 patients had > 20% circulating plasma cells. The remaining two had circulating plasma cells of 10% and 14% meeting the newly re-worked definition of plasma cell leukemia. One patient had a single extramedullary plasmacytoma at the time of diagnosis. High risk cytogenetics, defined as having t(4;14), t(14;16), t(14;20), Del17p, Gain1q, were characterized for all patients. 4 had one high risk mutation, 3 had two mutations. Only one patient’s first line did not include any of the novel therapies. 81% of patients’ first line of therapy included a form of cytotoxic chemotherapy (of which 55% of those were cisplatin, doxorubicin, cyclophosphamide, etoposide (PACE)). The most common first line of therapy was bortezomib (V), dexamethasone (D), PACE, +/- thalidomide (T) or lenalidomide (R), and +/- stem cell transplant (SCT). The other 19% of first line therapies contained exclusively novel therapies; namely VTD and daratumamab-RVD. Seven patients underwent SCT. One patient who underwent allogeneic transplant as part of their first line therapy has not yet relapsed 5 years post-transplant. Median OS was 28.8 months (95% CI 17.3 –not reached (NR)). First progression free survival (PFS) was 5.7 months (95% CI 2.3 – NR). For patients with available data, overall response rate (ORR) to 1st line of therapy was 60%. Conclusions: Our results demonstrate that the outcomes of patients with PCL have greatly improved with the use of novel therapies. The small sample size and heterogeneity of the treatments prohibited correlative statistical analysis. Prospective studies are needed to determine the best treatment option for this high-risk population which is excluded from most myeloma trials.