gms | German Medical Science

Background: Check-point targeted monoclonal antibodies have improved tumour-response-rates in numerous metastatic malignancies. Yet, disinhibition of immunity can have fatal consequences. Here, we report a case of a 68-year old male patient with metastasized castration resistant prostatic cancer on Pembrolizumab-(anti-PD-1)-Enzalutamide-combination therapy.

Methods: This is where he developed a severe condition, with continuous high-grade fever, mild splenomegaly, elevated liver enzymes, pancytopenia with low NK-cell counts, high levels of serum ferritin (73000 ng/ml) and soluble IL-2 receptor (20098 U/ml), without rash or neurological symptoms. Subsequently, bone marrow histology confirmed secondary hemophagocytic lymphohistiocytosis (HLH). Additionally, there were dense medullar polyclonal T-cellular infiltrates and reactive expansion of thrombocyte- and granulocytic progenitors.

Results: Paralleling initial antibiotic, anti-fungal therapy and discontinuation of pembrolizumab, the patient underwent daily plasmapheresis. Constitutional symptoms and fever, but not pancytopenia, responded rapidly to plasmapheresis administration. Ciclosporin and Etoposide were added for immunosuppressive treatment. After an initial increase in platelet and leukocyte counts, these fell again. Ciclosporin, of which no sufficient trough level was build up, was switched to Tacrolimus. The follow up bone marrow biopsy showed decreased T-cellular infiltrates and little evidence of phagocytosed material. Further plasmapheresis treatments could be dispensed with. 7 weeks after admission, the patient left the hospital with mild functional residuals, normalized leucocyte and thrombocyte counts, and mild anemia (Hb=11.2 g/dl).

Conclusion: Considering the bone marrow histology and since HLH has been reported on Pembrolizumab but not Enzalutamid-treatment in a metastasized setting, we suggest, that observed HLH had been triggered by PD-1 check point inhibition. We further provide a feasible protocol for successful short-term treatment of this condition. Lastly, this case underlines the importance of including “secondary HLH” in differential diagnostic considerations in adults with severe febrile disease, where even experienced clinicians might go with “sepsis” too early.