Immunohistological profiling by B-cell differentiation status of primary central nervous system lymphoma treated by high-dose methotrexate chemotherapy

Primary central nervous system lymphoma (PCNSL) remains a devastating disease with poor prognosis, despite the improvement offered by methotrexate (MTX)-based chemotherapy. Several studies have attempted to identify biomarkers predictive of prognosis, which are expected to be both clinically useful and biologically important for understanding PCNSL. The present study attempts to classify human immunodeficiency virus (HIV)-unrelated PCNSL patients treated with radiation combined with rapid high-dose MTX chemotherapy according to B-cell differentiation status, and retrospectively examines the prognostic impact. Initial response to MTX was a strong predictor of favorable prognosis in terms of both progression-free survival (PFS) and overall survival (OS). Thirteen out of 29 cases were CD10(-)/BCL-6(+)/MUM-1(+), being more frequent compared with systemic peripheral nodal lymphoma. Although post-germinal-center B-cell-originating PCNSLs (CD10(-)/BCL-6(-)/MUM-1(+)) showed a trend towards better response to MTX and progression-free survival than did germinal-center-related B-cell-originating PCNSLs (CD10(+) OR CD10(-)/BCL-6(+)/MUM-1(+)), the difference was only marginal (P = 0.04 Gehan-Breslow-Wilcoxon, P = 0.17 log-rank). Our results imply that different B-cell stages in PCNSL have significant relevance in terms of biological behavior. However, clinical use as a prognostic marker requires further investigation.