Review Question - QID 215147

A 62-year-old man presents to his primary care physician with fatigue and unintentional weight loss. Over the past month, he has felt increasingly tired during the day and has noticed that he has lost 15 lbs without any significant changes to his diet. His past medical history is significant for coronary artery disease, hyperlipidemia, and depression beginning after the loss of his spouse last year. Temperature is 98.6°F (37°C), blood pressure is 136/84 mmHg, pulse is 84/min, and respirations are 12/min. On exam, there is cervical, axillary, and inguinal lymphadenopathy. Abdominal exam shows hepatosplenomegaly. Complete blood count is as follows:

Hemoglobin: 9.8 g/dL
Hematocrit: 29.4%
Leukocyte count: 42,000/mm^3 with 90% lymphocytes
Platelet count: 80,000/mm^3

Genetic testing shows no tumor protein P53 (TP53), del(17p), or immunoglobulin heavy chain gene (IGHV) mutations. Which of the following is an appropriate initial therapy for this patient?