Multicenter Analysis of Outcomes in Blastic Plasmacytoid Dendritic Cell Neoplasm Offers a Pre-Targeted Therapy Benchmark

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an uncommon hematologic malignancy with poor outcomes. Existing data on the clinical behavior of BPDCN are limited because reported outcomes are from small retrospective series and standardized treatment guidelines are lacking. The IL-3 cytotoxin conjugate tagraxofusp was recently tested in Phase 1/2 trials that led to U.S. Food and Drug Administration approval, the first ever for BPDCN. However, since there was no matched internal comparator in this or any clinical study to date, results of BPDCN trials testing new drugs are difficult to compare with alternative therapies. We therefore sought to define the clinical characteristics and outcomes of a group of patients with BPDCN treated at three U.S. cancer centers in the modern era but before tagraxofusp was available. In 59 studied patients with BPDCN, the median overall survival from diagnosis was 24 months and outcomes were similar in patients with "skin only" or with systemic disease at presentation. Intensive first-line therapy and "lymphoid-type" chemotherapy regimens were associated with better outcomes. Only 55% of patients received intensive chemotherapy, and 42% of patients underwent stem cell transplantation. Clinical characteristics at diagnosis associated with poorer outcomes included age over 60, abnormal karyotype, and TdT negativity in the BPDCN cells. We also identified disease responses to pralatrexate and enasidenib in some patients. This study highlights poor outcomes for BPDCN patients in the modern era and the need for new treatments. Outcomes from ongoing clinical trials for BPDCN can be evaluated relative to this contemporary cohort.