A 55-year-old man presents to the clinic with a 3-month history of fatigue, weight loss, and night sweats. He has no significant past medical history. On examination, he has palpable lymphadenopathy in the cervical and axillary regions. Blood tests reveal a hemoglobin level of 10 g/dL, white blood cell count of 15,000/mm³ with a predominance of lymphocytes, and a platelet count of 150,000/mm³. A lymph node biopsy is performed, showing small lymphocytic lymphoma. What is the most appropriate initial management for this patient?