Bone formation following lenalidomide-dexamethasone combination therapy in cases of multiple myeloma refractory to high-dose chemotherapy with bortezomib and autologous peripheral blood stem cell transplantation: report of a case and review of the literature.

A 41-year-old man presented with the chief complaint of right hip pain that had persisted for 6 months. F18-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging showed FDG accumulation in the right pubic bone. A bone biopsy specimen from the site revealed findings suggestive of a plasma cell tumor. Bone marrow examination and serum and urine immunofixation tests showed no abnormalities. Based on these findings, the patient was diagnosed as having non-secretory multiple myeloma. FDG accumulation in the right pubic bone diminished following four cycles of weekly bortezomib and concomitant dexamethasone therapy. Tandem autologous peripheral blood stem cell transplantation was performed, followed by monthly bortezomib/dexamethasone maintenance therapy. A further FDG-PET/CT scan 9 months after the start of therapy indicated that FDG accumulation in the right pubic bone had worsened. Consequently, the therapy was switched to twice-weekly bortezomib/dexamethasone as remission re-induction therapy. New FDG uptake in the right hip bone was noted after six cycles of the therapy, and plain X-ray examination revealed osteolytic changes. The patient was then administered eight cycles of combined lenalidomide-dexamethasone therapy, which resulted in a marked decrease of the FDG accumulation in the right pubic bone and disappearance of uptake in the right hip bone. There was radiographic evidence of bone formation at these sites. This is only the second reported case in which treatment with the immunomodulatory drug lenalidomide and concomitant dexamethasone has been found to induce bone formation.