Relapse of tagraxofusp treated blastic plasmacytoid dendritic cell neoplasm with loss of CD123 expression

Tagraxofusp, a CD123-based-targeted immunotherapy, was recently approved to treat blastic plasmacytoid dendritic cell neoplasm (BPDCN) with excellent response. Also, a subset of BPDCN shows resistance to tagraxofusp. These resistant cases continue to express CD123, which forms the basis of the continued utility of tagraxofusp in newer combination chemotherapies to overcome resistance in BPDCN. Herein, we report a case of an elderly male with BPDCN that achieved complete remission on initial primary treatment with tagraxofusp. However, BPDCN relapsed after 1.5 years while on treatment, with loss of CD123 expression. At relapse, the neoplasm was comprehensively immunophenotyped by flow cytometry (performed on both peripheral blood and bone marrow specimen) and by immunohistochemical evaluation of the bone marrow clot section. The neoplasm at relapse was diagnostic of BPDCN with a lack of CD123 expression. This case highlights a potential limitation of current and upcoming tagraxofusp-based multidrug therapies, at least in a subset of refractory BPDCN. We believe our report will serve as a sentinel to incite future investigations involving alternate resistance mechanisms in BDPCN.

Serum thymus and activation-regulated chemokine (TARC) levels in newly diagnosed patients with Hodgkin lymphoma: a new promising and predictive tool? Preliminary report

Thymus and activation-regulated chemokine (TARC) is expressed on Reed-Sternberg cells of patients with classical Hodgkin lymphoma (HL) and may serve as a marker in response assessment. In our study, we correlated serum TARC levels with early response to treatment measured by PET/CT in 19 newly diagnosed patients with HL who received ABVD (Adriblastin, Bleomycin, Vinblastine, Dacarbazine) regimen. Finally, 17 patients were analyzed and six of them (35%) achieved PET/CT negativity defined as Deauville (D) 1 or 2 after 2 cycles of ABVD; 11 pts (65%) had D3 on PET/CT. None of the patients presented D 4/5. Median serum TARC levels at diagnosis were significantly higher when compared with healthy controls: 5718 pg/ml vs 76.1 pg/ml (p < 0.001). All study patients were treated with ABVD regimen and there was a significant decrease of baseline serum TARC levels after 2 cycles of therapy. No significant difference of baseline serum TARC levels was demonstrated between patients with D1/2 and D3 whereas levels were significantly decreased after 2 cycles of ABVD in patients D1/2 vs D3; p = 0.049. There was a tendency to higher baseline serum TARC levels in patients with an increased LDH (lactate dehydrogenase) activity (p = 0.08) and in those who progressed when compared with those who maintained response (p = 0.09). Serum TARC levels decrease after chemotherapy and may serve as a marker of response assessment.