FCRL2 is a stable indicator of IGHV mutation status and can predict time from diagnosis to initial treatment. (A) FCRL2 expression strongly correlates with the IGHV mutation status of 107 CLL samples. Cells were stained as previously with the biotinylated 7F2 mAb or an isotype-matched control followed by SA-PE, and the FCRL2 MFI ratio was derived from the gated CD19+CD5+ population. The horizontal line indicates the 4.2 MFI ratio cutoff value. (B) FCRL2 surface expression on CLL cells is stable over time. MFI ratios were determined for 16 CLL samples (8 MT, ●; 8 UM, ○) at multiple time points (2-5) over a 39-month interval. The stability of FCRL2 expression was evaluated using the overall concordance correlation coefficient (CCC).51 Values greater than 0.60 suggest satisfactory stability; those greater than 0.80 indicate excellent stability based on criteria established for the K coefficient.52 (C) FCRL2, IGHV, ZAP-70 T/B-CLL ratio, and CD38 can predict time from diagnosis to initial treatment. The median time to initial therapy for patients with high FCRL2 expression (MFI ratio ≥ 4.2) was 15.5 years compared with 3.75 years for patients with low FCRL2 expression (MFI ratio < 4.2). The median time to first therapy for patients with MT-CLL was 13.5 years versus 3.51 years for patients with UM-CLL; for ZAP-70 T/B-CLL ratio of 4.0 or greater it was 13.4 years versus 4.25 years for ZAP-70 T/B-CLL ratio less than 4.0; and for CD38 less than 30%, it was 9.92 years versus 3.34 years for CD38 of 30% or greater. P values are indicated in each panel.
