Prognostic value of pretreatment serum soluble interleukin-2 receptor levels in primary central nervous system lymphoma: a single-center retrospective study

Primary central nervous system lymphoma (PCNSL) is an aggressive disease with heterogeneous clinical outcomes, and readily measurable prognostic biomarkers remain limited. We retrospectively analyzed 21 patients with newly diagnosed PCNSL who received high-dose methotrexate-based therapy at a single institution between 2006 and 2023. The median age was 68 years, and 12 patients had deep-structure involvement. Median overall survival (OS) and progression-free survival were 41 and 31 months, respectively. In univariate analyses, pretreatment serum soluble interleukin-2 receptor (sIL-2R) level (p = 0.0185), cerebrospinal fluid protein level (p = 0.0401), and receipt of radiotherapy (p = 0.0377) were significantly associated with OS. Receiver operating characteristic analysis of pretreatment serum sIL-2R for 3-year OS yielded an area under the curve of 0.869; a candidate threshold of 566 U/mL showed a sensitivity of 85.7% and specificity of 83.3%. Pretreatment serum sIL-2R was associated with OS in this small retrospective cohort, and this exploratory finding warrants validation in larger independent studies.