A preliminary study by Aue et al.  highlighted the potential utility of sFLCs for monitoring CLL. Prior to treatment, a total of 8/11 patients with a κ CLL clone had κ sFLC concentrations above the normal range. After 6 months of ibrutinib therapy, there was a 76% reduction in κ sFLCs (p<0.01), and in 7/8 patients sFLC concentrations had normalised. By contrast, λ FLCs were initially low and then increased to normal levels following therapy. Similar findings were reported for 8 of 9 patients with a λ clone. The authors suggested that sFLC monitoring might provide an insight into both the killing of the tumour cells and the recovery of normal B-cell function.