A new prognostic model using absolute lymphocyte count in patients with primary central nervous system lymphoma

Purpose Primary central nervous system lymphoma (PCNSL) is an aggressive and rare extranodal non-Hodgkin lymphoma (NHL). Absolute lymphocyte count (ALC) has been suggested to have a prognostic value in several subtypes of NHL. We evaluated the prognostic significance of clinical factors, including ALC, in patients with PCNSL to develop a new prognostic model. Methods We analysed prognostic factors, including ALC, at diagnosis in 81 PCNSL patients receiving high-dose methotrexate-based therapy. Results The median ALC at diagnosis was 1210 × 10⁶/L (range, 210–3610), with lymphopenia (≤875 × 10⁶/L) being detected in 27 (33.3%) patients. In the multivariate analysis, Eastern Cooperative Oncology Group performance status (ECOG PS) >1 (hazard ratio [HR] 3.18, P = 0.003), age >50 years (HR 4.23, P = 0.012), and lymphopenia at diagnosis (HR 2.83, P = 0.008) remained independent prognostic factors for low overall survival (OS). Lymphopenia was also a significant prognostic factor for progression-free survival (HR 3.17, P = 0.001). By means of a new three-factor prognostic model using ECOG PS >1, age >50 years, and presence of lymphopenia, with 1 point assigned to each factor, we successfully classified the patients into three risk groups: low (0 and 1), intermediate (2), and high (3). The 5-year OS rates of the patients in the low-, intermediate-, and high-risk groups were 74.3%, 21.7%, and 12.5%, respectively (P < 0.001). Conclusions Low ALC is a useful indicator of poor prognosis in patients with PCNSL. The proposed three-factor model should be validated in large-scale studies.