Successful nivolumab therapy in an allogeneic stem cell transplant child with post-transplant lymphoproliferative disorder.

Primary CNS PTLD is an extremely rare complication after allogeneic HSCT. At our centre, an 11-year-old patient developed nausea, vomiting, and diplopy on day +82 following HSCT. On brain MRI, multiple white matter lesions were seen. Histology showed a diffuse large B-cell lymphoma with high load of EBV in tissue. Despite stopping immunosuppression, treatment with EBV-specific cytotoxic T cells, systemic rituximab, HD-MTX, and intrathecal chemotherapy, progression was observed. With a combination of HD-MTX and cytarabine, only a partial response could be achieved. Having all conventional modalities not only failed but resulted in significant toxicity, a salvage monotherapy with biweekly nivolumab has been instituted. The starting dose was 1.1 mg/kg, later escalated to 2.2 mg/kg. After 8 months of nivolumab therapy, PET-CT showed complete metabolic remission. Subsequently, the patient has been switched to a maintenance dosage of 1.1 mg/kg. No cytopenias, graft failure, GvHD, or any other alloimmune complications were seen during nivolumab therapy. In conclusion, nivolumab may be considered as an effective and safe option for CNS PTLD therapy when all other modalities have failed.