Complete remission achieved in a multiple myeloma patient with elevated serum KL-6 level by a combination regimen with bortezomib, cyclophosphamide, and dexamethasone.

A 79-year-old woman suffering from double vision after a 4-year history of MGUS was referred to our hospital. MRI revealed that she had three intracranial plasmacytoma masses and one spinal plasmacytoma mass. Bone marrow aspirates showed 52.4% plasma cell infiltration and immunoelectrophoresis identified serum IgG-M protein, leading to a diagnosis of IgG-type multiple myeloma. IgG was elevated to 3,355 mg/dl and urine type Bence-Jones protein was positive. KL-6, a membrane-bound glycoprotein encoded by Mucin 1 and a marker of interstitial pneumonia, was also elevated to 1,409 mg/dl, but computed tomography of the lungs revealed no obvious pulmonary lesions. Previously reported studies showing that myeloma patients with elevated KL-6 might have a poor prognosis prompted us to treat this patient with a three-drug (bortezomib, cyclophosphamide, and dexamethasone: VCD) combination regimen. When 6 cycles of the regimen had been completed, no M-protein was detectable in her serum. Furthermore, κ free light chain had significantly decreased from 12,700 to 24.8 mg/l. In addition, (18)F-FDG PET/CT revealed reduced mass sizes and no (18)F-FDG uptakes by plasmacytomas. Thus, she was defined as having achieved a stringent complete remission (sCR). We therefore concluded that the VCD combination regimen was highly effective in this multiple myeloma patient with KL-6 elevation.