Soluble TACI and soluble BCMA as biomarkers in primary central nervous system lymphoma.

BACKGROUND: B-cell survival is regulated through interactions of B-cell-activating factor and a proliferation-inducing ligand with their receptors transmembrane activator and CAML interactor (TACI) and B-cell maturation antigen (BCMA). We evaluated the diagnostic potential of soluble TACI (sTACI) and soluble BCMA (sBCMA) in CSF and serum as biomarkers in primary CNS lymphoma (PCNSL). METHODS: CSF (n = 176) and serum samples (n = 105) from patients with clinically or radiologically suspected PCNSL as well as from control patients were collected prospectively. Levels of sTACI and sBCMA were analyzed by enzyme-linked immunosorbent assay. Additionally, in patients with PCNSL, CSF was analyzed during disease course (time of diagnosis, n = 26; relapse, n = 10; remission, n = 14), and in 2 patients long-term longitudinal analysis was performed. RESULTS: Soluble TACI and sBCMA are significantly increased in patients with PCNSL (sTACI, median: 445 pg/mL; sBCMA, median: 760 pg/mL) compared with control patients (sTACI, median: 0 pg/mL; sBCMA, median: 290 pg/mL). At a cutoff value of 68.4 pg/mL, sTACI shows high sensitivity (87.9%) and specificity (88.3%) for the diagnosis of active PCNSL. Soluble BCMA is less sensitive (72.7%) and specific (71.8%) (cutoff: 460 pg/mL). When both markers are combined, specificity increases, however, at the cost of a lower sensitivity. In serum, both sTACI and sBCMA are not increased in PCNSL patients. Both soluble receptors correlate with clinical course and therapy response. CONCLUSIONS: Our results suggest that sTACI and sBCMA in the CSF are promising new biomarkers for diagnosis and therapy monitoring in PCNSL. However, our findings need to be validated in an independent cohort.