Many studies have indicated that the reduction in sFLCs after one or two cycles of treatment is highly predictive of overall response. For example, Dispenzieri et al.  reported that a 90% reduction in sFLCs (90% reduction in the difference between the involved and uninvolved FLC [dFLC]) within 7 days post-ASCT predicted for haematologic complete response (p<0.001). Other studies have similarly highlighted the value of early sFLC reductions in predicting overall response . Looking at a different measure of outcome, Orlowski et al.  reported that rapid normalisation of the FLC κ/λ ratio - after the first or second cycle of therapy - was highly predictive of prolonged time to progression. The prognostic value of the sFLC response is discussed further in Chapter 20.