Promising Effect of PDL1 Inhibitors in PCNSL

Abstract

PCNSL or secondary CNSL both are associated with poor prognosis & inferior survival, and some cases are refractory to currently available lines of treatment. PDL1 inhibitors started to emerge in the literature as a new line of treatment in this disease entity. The programmed death ligand PD-L1 negatively regulate immune response & promote escape of tumor cells from immune surveillance, PD1 is expressed on T lymphocytes, including tumor infiltrating lymphocytes (TILs), while PDL1 expression is found on antigen presenting cells & on tumor cells in various cancer types, including some lymphomas. Binding of PDL1 to PD1 inhibits the proliferation of activated T lymphocytes & thus the anti-tumor adaptive immune response. In this case we evaluated the effect of PDL1 inhibitor Nivolumab in PCNSL refractory to 1st line (high dose MTX/AraC-Rituximab). Efficacy was evaluated using MRI which showed complete remission following 4 bi-weekly cycles, maintained complete remission on repeated evaluation after 10th & 14th cycles. The patient was shifted to monthly doses. The patient tolerated the treatment well apart of mild elevation of trans-aminases. Time to treatment failure was not reached till time of submission of this abstract (8 months). PDL1 Inhibitors showed effective clinical and radiological response in PCNSL. Further studies are needed to assess this point and follow up to assess the time to treatment failure. The remaining un-answered question is: How to consolidate the achieved response? DisclosuresNo relevant conflicts of interest to declare.