Table 4 Definition of treatment responses

Complete response (CR)

Complete disappearance of all previously observed abnormalities on radiographic imaging. For patients with a secretory plasmacytoma, a disappearance of monoclonal protein from serum and/or urine. For SBP, the initial radiological abnormalities on MRI or CT should regress or stabilize during an observation time of at least 12 months to fulfill the requirements for a CR. For EMP, the disappearance of soft tissue mass is required for the definition of CR

Very good partial response (VGPR)

A CR with regard to clinical and radiological signs, but with a positive immunofixation or ≥ 90% reduction in serum monoclonal protein plus urine monoclonal protein level < 100 mg/24 h.

Partial response (PR)

A ≥ 50% decrease in serum and/or urine monoclonal protein. For non-secretory SP, radiological features (MRI/CT) or local assessment is needed. In EMP patients, a 30% decrease in the diameter of target lesions should be observed.

Stable disease (SD)

Insufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD.

Progressive disease (PD)

The development of new lesions or an increase of at least 20% in the size of existing lesions, the apparition of a myeloma defining event, and finally an increase of > 25% from lowest response value in serum and/or urine monoclonal protein.