Prognostic value of circulating lymphocyte subsets in primary central nervous system lymphoma

Background Immunity plays an important role in CNS-DLBCL development. CNS-DLBCL predictive factors need to be improved. Objective To evaluate the predictive value of circulating lymphocyte subsets in PCNSL patients. Methods We prospectively analyzed blood lymphocyte immunophenotyping (LIP) in newly CNS-DLBCL referred to our institution between December 2013 and January 2020. LIP analysis was performed before rituximab and chemotherapy administration. The clinical, radiological, histological, biological and treatment data were retrospectively collected. Results Fifty-three patients were included with a median age of 69.7 (range 21.7–87.5). Median KPS was 60 (range 30–100). Thirty-three patients (64%) presented with one or several lymphopenias: 21 (40%), 24 (46%) and 9 (17%) NK, T and B lymphopenias respectively. Only 11 patients (21%) had normal LIP. Median CD4+/CD8+ ratio was 2.11 (range 0.54–9.11). This ratio was normal, low or high in 27%, 28% and 44% of patients respectively. The presence of steroids did not impact LIP results. Complete, partial responses, stable and progressive disease (PD) were observed in 24 (50%), 10 (21%), 4 (8%), and 10 (21%) patients respectively. CD4+/CD8+ ratio tended to be different between refractory (PD patients) and non-refractory patients (p = 0.077, ROC AUC: 0.684). Median progression-free survival (PFS) and overall survival (OS) were 14.7 (95%CI 6.5–22.9) and 43.2 (95%CI 21.6–64.9) months, respectively. In multivariate analyses, adjusted by KPS, a CD4+/CD8+ ratio > 1.97 was associated with poor PFS [p = 0.043, HR = 3.32 (1.02–4.88)] and tended to be associated with worse OS (p = 0.064). Conclusion LIP at baseline may predict refractory disease and exhibits a prognostic value in CNS-DLBCL patients.