Case Report of Anti-CD123 Chimeric Antigen Receptor T-Cell Therapy Followed by Radiotherapy for a Recurrence of Blastic Plasmacytoid Dendritic Cell Neoplasm After Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematopoietic malignancy. There is no standard chemotherapy regimen for BPDCN, and even allogeneic hematopoietic stem cell transplantation (allo-HSCT) has not been able to extend the survival of patients with BPDCN. CASE REPORT: Here, we present a case of recurrence of BPDCN in a patient with new nodules in his head six months after allo-HSCT. He was enrolled in a clinical trial of anti-CD123 chimeric antigen receptor (CAR) T-cell therapy (ChiCTR1900022058). However, there were no significant changes in the nodules 28 days after anti-CD123-CAR T-cell infusion. He received radiotherapy for the nodules when the proportion of anti-CD123-CAR T-cells in the peripheral blood was 2.8% and the adverse events related to the anti-CD123-CAR T-cell therapy were resolved. The proportion of anti-CD123-CAR T-cells, the level of CD123-CAR gene desoxyribonucleic acid, and the serum levels of cytokines in the patient’s peripheral blood reached the highest peak 14 days after radiotherapy. Fortunately, the nodules disappeared gradually 28 days after radiotherapy. He achieved complete remission again from the anti-CD123-CAR T-cell therapy followed by radiotherapy. To date, he has maintained progression-free survival with complete donor chimerism for six months after the combination therapy. CONCLUSION: Anti-CD123-CAR T-cell therapy followed by radiotherapy for a recurrence of blastic plasmacytoid dendritic cell neoplasm after allo-HSCT is effective.