Review Question - QID 108631

A 72-year-old man presents to the primary care clinic for evaluation of a 1 month history of progressive fatigue and weight loss. His past medical history is significant for hypercholesterolemia, type 2 diabetes mellitus, aortic stenosis, and chronic renal insufficiency. He endorses being well-rested after waking from sleep but rapidly becoming fatigued during the day. In addition, he states that he has lost 15 lbs over the previous month. His temperature is 98.3°F (36.8°C), pulse is 100/min, blood pressure is 110/85 mmHg, respirations are 16/min, and oxygen saturation is 96% on room air. Physical exam is notable for conjunctival pallor and scattered areas of ecchymoses. His laboratory results are shown below:

Serum:
Na+: 140 mEq/L
K+: 4.0 mEq/L
Cl-: 101 mEq/L
HCO3-: 22 mEq/L
BUN: 30 mg/dL
Glucose: 160 mg/dL
Creatinine: 1.9 mg/dL

Leukocyte count: 1,100/mm^3
Absolute neutrophil count 920/mm^3
Hemoglobin 8.4 g/dL
Platelet count: 45,000/mm^3
Mean corpuscular hemoglobin concentration: 34%
Red blood cell distribution width: 12.0%
Mean corpuscular volume: 92 µm^3
Lactate dehydrogenase: 456 IU/L
Haptoglobin 120 mg/dL
Fibrinogen 214 mg/dL

A bone marrow biopsy is performed which shows cells that are CD19+, CD20+, CD11c+, and stain with acid phosphatase 5 and tartrate-resistant. Which of the following is the next best step in the treatment of his disorder?