Q. A 65-year-old man comes to his physician’s office for increasing fatigue and bone pain for the past 6 months. He also complains of frequent respiratory infections and usage of antibiotics in this time period. His temperature is 99°F (37.2°C), heart rate is 100/min, respiratory rate is 14/minute, and blood pressure is 130/70 mm of Hg. Physical examination shows tenderness over the lower back. Laboratory tests are shown below. Serum protein electrophoresis shows a monoclonal spike in the gamma-globulin region. Urine protein electrophoresis reveals Bence Jones proteins. A skeletal survey shows multiple lytic lesions. What is the next best step in the management of this patient's condition?