Single center retrospective evaluation of CHOP-based regimens in older patients with treatment naive blastic plasmacytoid dendritic cell neoplasm

Abstract BACKGROUND: Blastic plasmacytoid dendritic cell neoplasm (BPCDN) is an extremely rare and aggressive hematologic malignancy. Several chemotherapeutic approaches have been described as induction strategies for BPDCN. The approval of tagraxofusp-erzs, a CD123-directed cytotoxin, for treatment naïve or relapsed/refractory BPDCN was based on a single-arm phase II study, but many patients may not qualify for this due to hypoalbuminemia or other co-morbidities. Optimal treatment remains under investigation, especially in the setting of older and unfit patients, with allogenic hematopoietic stem cell transplant (allo-HCT) being the only potentially curable treatment option available. The CHOP regimen is available worldwide, has historical long-term use in lymphoma, and has been applied to patients with BPDCN globally. Since CHOP-based regimens involve older, generic medications and BPDCN is a rare diagnosis, it was unlikely that these two induction strategies would be compared in prospective fashion, but the financial impacts and clinical complexity of tagraxofusp-erzs requires that alternative therapies that may provide an avenue to allo-HCT be reported. METHODS: We report the clinical outcomes of a single center, retrospective analysis of patients with treatment naïve BPDCN treated with CHOP-based induction regimens between January 1996 and February 2023. Patients were identified using the University of Michigan EMERSE database and keywords. The primary endpoint was a composite of complete remission rate and complete remission with incomplete count recovery after induction chemotherapy. Secondary endpoints included short-term efficacy outcomes including complete response (CR), complete response with incomplete count recovery (CRi), partial response (PR), and overall response rates (ORR) and long-term efficacy outcomes including event-free survival (EFS) and overall survival (OS). RESULTS: Of the 12 patients treated, 92% (11 out of 12) achieved a partial response. 50% (6 out of 12) achieved CR or CRi after induction therapy. Of those patients, 4 received hematopoietic stem cell transplant (HCT) with 3 receiving allo-HCTs and 1 receiving an auto-HCT. Mean overall survival rate for the entire cohort was 16.4 months (95% CI 12.8 – 20). For those who received HCT, overall survival was 27.8 months (95% CI 9.8 – 48.8). CONCLUSION: In this series, the major driver in improvement in overall survival difference appears to be younger age and ability to proceed to allo-HCT. Although limited by retrospective design and small number of patients, this study suggests CHOP-based induction strategies achieve remission rates similar to those obtained with tagraxofusp-erzs for treatment naïve BPDCN and may be considered as a potential frontline therapy for older patients with BPDCN.