A 73-year-old man was diagnosed as having multiple myeloma (MM), with serum protein electrophoresis (SPEP) and immunofixation (IF) showing a monoclonal (M) IgA κ at 0.3 g/dL and serum free κ/λ ratio skewed at 257. A computed tomographic scan showed lytic lesions, and bone marrow biopsy findings revealed 30% κ-restricted plasma cells. He was assigned to the bortezimib-lenalidomide-dexamethasone–elotuzumab (VRD-E) arm of a phase 3 trial. Three weeks after therapy initiation, follow-up SPEP-IF demonstrated an M-IgA κ at 0.1 g/dL. Two months later, SPEP-IF demonstrated a new M-IgG κ band in the same electrophoretic position as the M-IgA κ, with the 2 distinguishable only by IF and measured at 0.1 g/dL. Three months later, SPEP-IF demonstrated only the M-IgG κ, with the original M-IgA κ not detected. Over the next 8 months, the patient received maintenance therapy with VRD-E, and monthly SPEP-IF consistently showed M-IgG κ at 0.1 g/dL, with the original M-IgA κ consistently not detected. The serum free κ/λ ratio gradually decreased to 4.86 one year later. The Table summarizes assay data.
Tang F, Schmotzer C, Beck RC. A New Monoclonal Protein Detected in a Patient With Myeloma Undergoing Elotuzumab Therapy. JAMA Oncol. Published online September 07, 2017. doi:10.1001/jamaoncol.2017.2665