Monitoring with sFLCs allows early detection of ineffective treatment, and the identification of patients who may benefit from alternative chemotherapy regimens. One such example is shown in Figure 18.8
In this patient with IgGλ MM, the sFLC concentration initially decreased in response to treatment, with a negligible corresponding change in IgG concentration. Subsequently, λ sFLC levels stabilised, indicating that the patient was no longer responding to treatment. This was in contrast to the IgG levels, which were continuing to fall, suggesting a continuing response. Only after several months did IgG levels start to increase, signifying a tumour regrowth.