[Perspectives on Precision Medicine in Primary Central Nervous System Lymphoma]

Primary central nervous system lymphoma(PCNSL)is an aggressive, extranodal non-Hodgkin lymphoma that arises from the central nervous system, eyes, leptomeninges, and the spinal cord. Most PCNSLs are a type of diffuse large B-cell lymphoma(DLBCL), and the majority are categorized as a non-germinal center B-cell(GCB)subtype. Recent genetic studies have revealed several common genetic abnormalities in PCNSL, such as MYD88 and CD79B mutations, suggesting dependence on the B-cell receptor/Toll-like receptor signaling pathway. These genetic findings have rationalized targeted therapy targeting Bruton's tyrosine kinase(BTK), a key molecule of the B-cell receptor pathway in PCNSL and systemic non-GCB DLBCL. The first-generation BTK inhibitor ibrutinib has been widely studied in clinical trials for PCNSL and systemic non-GCB DLBCL. In Japan, a second-generation BTK inhibitor tirabrutinib was studied in a phase I/II trial and approved by the Japanese Ministry of Health and Welfare in March 2020 for relapsed and refractory PCNSL. While the current standard-of-care therapy for PCNSL is methotrexate(MTX)-based multi-agent induction immunochemotherapy like R-MPV(rituximab, MTX, procarbazine, and vincristine)followed by consolidation chemotherapy and/or radiation therapy, further investigation into the optimal use of BTK inhibitors in the standard-of-care therapy of PCNSL is warranted.