5.A 73-year-old man has been on active surveillance for CLL for the past 5 years. He presents for routine follow-up and reports increasing fatigue, pallor, and lymph node swelling. Physical examination reveals increased splenomegaly. Laboratory values show a white blood cell count of 150K (84K 3 months ago), hemoglobin is 10.5 g/dL, and platelets are 75K. Previously, lymph node biopsy revealed del(17p)/TP53. What is the next best step?

A. Ibrutinib

B. Bone marrow aspiration and biopsy

C. Bendamustine and rituximab (BR)

D. Fludarabine, cyclophosphamide, and rituximab (FCR)