Outcomes of CNS involvement in blastic plasmacytoid dendritic cell neoplasm (BPDCN).

Abstract

e19043 Background: BPDCN is rare cancer commonly involving the skin and marrow. Tagraxofusp (Tag), a CD123 targeted therapy, was the first FDA approved drug for BPDCN in 2018. CNS involvement occurs in 10-60% of patients and CNS staging and prophylactic (ppx) practices are variable. The pivotal trial of Tag in BPDCN did not require CNS staging and excluded those patients with known CNS involvement. Here, we describe one of the largest cohorts of BPDCN patients with known CNS involvement, including patients treated with Tag. Methods: We collected data from 4 centers on patients with CNS involvement defined by LP or imaging with high clinical suspicion. Survival was estimated via the Kaplan-Meier method with other analyses being descriptive. Results: CNS involvement was identified in 11 patients. Median age was 74 (range 51–83) and 10 were male. 5 patients had CNS staging at initial diagnosis. At time of CNS involvement, 6/11 patients had neuro symptoms. Prior to diagnosis of CNS involvement, 5 received Tag and none received CNS ppx. Of 9 patients treated for their known CNS involvement (table), one received CNS directed systemic therapy, with all others being treated with intrathecal (IT) chemotherapy. All patients treated with 3 or more doses of IT chemotherapy cleared their CSF, and survived at least 6 months from the diagnosis of CNS involvement, including two patients (#5 and 8) with large burden CNS disease and neuro symptoms. Median survival from time of diagnosis of BPDCN was 13.8 months (2.7-35.5) and from time of diagnosis of CNS involvement was 6.0 months (0.1-25.7). Conclusions: Asymptomatic CNS involvement by BPDCN is common; routine staging and ppx should be considered at diagnosis. Tagraxofusp did not appear to prevent the development of CNS disease. IT therapy effectively cleared and controlled CNS involvement in a majority of patients. IT therapy may be sufficient to control CNS disease and IT prophylaxis should be considered, including in patients on CD123 targeting therapies. Our results provide new insights into BPDCN with CNS involvement and include patients treated with recently developed novel systemic therapies.[Table: see text]