BTK inhibitor combined with anti-PD-1 monoclonal antibody for the treatment of CD20-negative primary central nervous system lymphoma: A case report.

CD20-negative diffuse large B-cell lymphoma (DLBCL) is a rare type of lymphoproliferative disorder characterized by a high degree of aggressiveness, a tendency for extranodal invasion and chemotherapeutic resistance. CD20-negative DLBCL originating from the nervous system is rarer. In primary central nervous system lymphoma (PCNSL), >90% of cases are histologically classified as DLBCL. The present study reports the case of a 65-year-old female with CD20-negative PCNSL, whose primary clinical symptom was a persistent headache. Serum tests for human immunodeficiency virus, Epstein-Barr virus-DNA, human herpesvirus 8, hepatitis B and hepatitis C were negative. Cranial magnetic resonance imaging suggested multiple intracranial occupancies. The neoplastic cells were found to be positive for CD19, CD79α, Bcl-2 (~92%) and c-Myc (~50%), while showing negative results for CD20, CD138, programmed cell death protein 1 (PD-1) and programmed cell death receptor 1 ligand 1 (PD-L1). The Ki-67 proliferation index was >80%. In the tumor microenvironment, <10% of the tumor-associated macrophages expressed PD-L1. The number of PD-1-positive tumor-infiltrating lymphocytes was 30-40 cells according to high-power field microscopy. The patient's disease progressed during methotrexate-based treatment, leading to a change in the treatment regimen to the Bruton tyrosine kinase inhibitor, zanubrutinib, combined with the anti-PD-1 monoclonal antibody tislelizumab. After two courses of the combined treatment, the patient achieved complete remission (CR) and continued to receive consolidation treatment. In the 20 months of follow-up since CR was achieved, the patient's general condition was good and the disease was in continuous remission. The present case report and literature review show that a combination of drugs targeting different mechanisms may be used to treat PCNSL to prolong patient survival time. The mechanism of the enhanced efficacy of a combination of the two drugs may be related to the enhancement of antitumor T-cell immune responses and reversal of T-cell immune metabolic dysfunctions by the inhibition of glycolysis.