Table 5 Response Criteria for FLC36, 37

From: International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders

  Minimum to be deemed measurable PR CR sCR Progression
AL36 without measurablea serum or urine M protein iFLC 100 mg/l 50% reduction of iFLC Normal rFLC and CR by IFE and bone marrow ND 50% increase of iFLC to >100 mg/l
AL36 with measurablea serum or urine M protein ND ND ND ND ND
MM37 without measurablea serum or urine M protein iFLC 100 mg/l and rFLC abnormal 50% reduction of dFLC ND Normal rFLC & CR by IFE and bone marrow 50% increase of dFLC
MM with measurable disease12, 37 Use of FLC not recommended Use of FLC not recommended Use of FLC not recommended Normal rFLC & CR by IFE and bone marrow Use of FLC not recommended
  1. Abbreviations: dFLC, difference between iFLC and uninvolved FLC; iFLC, involved free light chain, that is, κ for a patient with κ restricted disease and λ for a patient with λ restricted disease; ND, not defined.
  2. aMeasurable M protein includes serum M protein of at least 1 g per 100 ml or a urine M-protein of at least 200 mg/24 h for myeloma patients (100 mg/24 h for AL patients).