Maurer et al. 
evaluated the use of sFLCs for monitoring DLBCL in the N0489 trial. Pre- and post-treatment (cycle 6) sFLC measurements were available for 11 patients with κ- or λ-restricted tumours. Analysis of these samples revealed that, post-treatment, a greater reduction in the involved sFLC concentration was observed compared with the uninvolved sFLC (p=0.03). Serial monitoring samples were available for one λ-restricted DLBCL patient (Figure 31.8.
. The pre-treatment levels of λ sFLCs were highly elevated, with normal levels of κ sFLCs. λ sFLCs normalised after two cycles of treatment and the patient achieved a PET-negative complete response after six cycles. However, at 9 months post-treatment, λ sFLCs had increased, and tumour imaging and biopsy confirmed disease relapse. κ sFLCs remained unchanged throughout. This case illustrates that changes in the DLBCL tumour itself may directly influence changes in the corresponding sFLC.