Usefulness of Serum Soluble Interleukin-2 Receptor Levels for Differentiating between PCNSL and SCNSL

Serum soluble interleukin-2 receptor (sIL-2R) is a practical tumor marker that is elevated in hematogenous tumors. The purpose of this study was to determine the usefulness of serum sIL-2R for differentiating among malignant brain tumors, including primary central nervous system lymphoma (PCNSL) and secondary central nervous system lymphoma (SCNSL). This study retrospectively investigated the sIL-2R levels in 130 patients with various types of malignant brain tumors, including PCNSL patients (n = 48) and SCNSL (n = 8); metastatic brain tumors (MTs, n = 16); and glioblastoma (GBM, n = 58). The median sIL-2R level (U/mL) of the PCNSL, SCNSL, MTs, and GBM groups were 489.7, 1024.8, 413.3, and 332.7 respectively. The sIL-2R level was significantly higher in the SCNSL group than in the PCNSL or other groups. The area under the ROC curve generated from the sIL-2R level was 0.826 (sensitivity: 0.875, specificity: 0.667, cutoff value: 521 U/mL) for differentiating SCNSL from PCNSL and 0.685 (sensitivity: 0.667, specificity: 0.707, cutoff value: 342 U/mL) for differentiating PCNSL from GBM. Measurement of sIL-2R level was convenient and useful to differentiate between SCNSL and PCSNL, both of which demand different treatment strategies.