Table 1.

Relevant IMWG Response Criteria (Adapted with permission from the original publication by Kumar S., et al. [3]).

Response	Definition
Complete response (CR)	Negative immunofixation in the serum or urine and disappearance of any soft tissue plasmacytomas and <5% plasma cells on bone marrow aspirate
Stringent Complete Response (sCR)	Complete response as defined above plus a normal serum free light chain ratio (FLC) and absence of clonal plasma cells on bone marrow aspirate
Very Good Partial Response (VGPR)	Serum and urine M-protein detectable on immunofixation but not on electrophoresis -or- >90% reduction in serum M-protein plus urine M-protein < 100 mg on 24 h collection
Partial Response (PR)	>50% reduction of serum M-protein plus > 90% reduction in or <200 mg per 24 h urine collection If serum and urine M-protein unmeasurable and FLC are also unmeasurable, >50% reduction in plasma cells is required in place of M-protein, provided that the baseline percentage in bone marrow is at least 30%. Additionally, a >50% reduction in the size of soft tissue plasmacytomas is also required as measured by FDG18-PET/CT
Minimal Response (MR)	≥25% but ≤49% reduction of serum M-protein and reduction in 24-h urine M-protein by 50–89% If soft tissue plasmacytoma is present, then >50% reduction in size is also required.
Stable Disease (SD)	Not meeting criteria for CR, VGPR, PR, MR, or PD. Generally, not recommended for use as an indicator of response
Progressive Disease (PD)	Increase of 25% from the lowest confirmed response value in one or more of the following criteria: Serum M-protein (absolute increased must be >0.5 g/dL) Serum M-protein increase ≥1 g/dL, if the lowest M component was ≥5 g/dL Urine M-protein (absolute increase must be ≥200 mg/24 h) In patients without measurable serum and urine M-protein levels, the difference between involved and uninvolved FLC levels (absolute increase must be >10 mg/dL) In patients without measurable serum and urine M-protein levels and without measurable involved FLC levels, bone marrow plasma-cell percentage irrespective of baseline status (absolute increase must be ≥10%) ≥50% increase in the size of >1 skeletal or soft tissue lesion, or ≥50% increase in the longest diameter of a previous lesion > 1 cm in short axis (as measured by FDG18 PET/CT) ≥50% increase in circulating plasma cells (minimum of 200 cells per μL) if this is the only measure of disease
Clinical Relapse	Any one or more of the following criteria: Direct indicators increasing disease and/or end-organ dysfunction (i.e., CRAB features) Development of new soft tissue plasmacytomas or bone lesions (excluding osteoporotic fractures) Definite increase in the size of existing plasmacytomas or bone lesions by >50% as measured by serial FDG18 PET/CT Hypercalcemia (>11 mg/dL) Decrease in hemoglobin of >2 g/dL not related to therapy or other non-myeloma conditions Rise in serum creatinine by 2 mg/dL or more from the start of therapy attributable to myeloma Hyperviscosity related to serum paraprotein
Relapse from CR	Any one or more of the following Reappearance of serum or urine M-protein by immunofixation or electrophoresis Development of >5% plasma cells in the bone marrow Appearance of any other signs of progression (ie. New plasmacytoma or CRAB features)