Epidemiology of plasma cell leukemia in the U.S.: Incidence, mortality and survival predictors.

Abstract

e19579 Background: Plasma cell leukemia (PCL) is a rare and aggressive disorder with poor survival outcomes. It is defined by the presence of >20% circulating plasma cells in the blood and/or > 2 × 109/L plasma cells in a peripheral blood smear. Management strategy includes a combination of immunotherapy, proteasome inhibitors, and high dose induction chemotherapy followed by immediate autologous hematopoietic stem cell transplant (HSCT). While this practice has proven benefit in multiple myeloma, there are no studies demonstrating its efficacy in PCL. Methods: We conducted a retrospective study using de-identified data from TriNetX, a U.S. based multi-institutional database to screen PCL patients from 2000 to 2020. We excluded patients who tested HIV positive, who did not undergo HSCT or started chemotherapy > 120 days after diagnosis to eliminate immortal time bias. We looked at the incidence of PCL, and calculated the 1-, 3- and 5-year survival data for PCL. We also analyzed the survival based on age, gender, ethnicity and plasma cell levels in the blood. Results: From 2000-2020, we identified 641 PCL patients who met the inclusion criteria. The mean age of PCL patients was 71. 52.42% patients were males and 45.08% patients were females. Most of the patients were Caucasian (64.43%) followed by African Americans, (20.74%). Only 3.59% patients were of Hispanic origin. The median follow up time was 5 years, and the corresponding median survival was calculated as 41 months. 1-year mortality was 72.41%, 3- year mortality was 53.52% and 5- year mortality reduced to 44.85%. Patients aged > 60 years were 1.5 times more likely to die as compared to those aged < 60 years [Odds ratio (OR) 1.91, p-value 0.02]. Male gender did not influence survival outcomes (OR 1.12, p-value 0.52). Similarly, ethnicity did not confer increased risk of mortality (OR for African Americans versus Caucasians was 1.06, p 0.80). Plasma cell levels also did not predict the risk of death. (OR for plasma cells>20% 1.27, p-value 0.72) Conclusions: Median survival of PCL patients has improved over the years to around 41 months. This can be attributed to the widespread use of proteasome inhibitors, high-dose chemotherapy and the autologous HSCT. Patients aged > 60 years have a worse survival outcome, whereas gender and ethnicity do not predict survival.