- For oligo- or non-secretory multiple myeloma, measurable disease is defined by the presence of soft tissue (not bone) plasmacytomas as determined by clinical examination or applicable radiographs (i.e. MRI, CT-Scan). In patients with oligosecretory multiple myeloma, the serum and/or urine M-protein measurements are very low and difficult to follow for response assessments. Therefore, other disease sites (bone marrow; extramedullary mass) must be assessed and followed. In patients with non-secretory multiple myeloma, there is no M-protein in serum or urine by immunofixation.