A 72-year-old man comes to the oncology clinic to discuss treatment options after the recent diagnosis of B-cell lymphoma; he is accompanied by his daughter. He reports that he is "fine but feels a little run down." His daughter reports that he is taking multiple naps daily. He has lost 9 kg (20 lb) over the last 6 months. He has fallen twice, without injury, in the last month. He does not use assistive devices to ambulate. Which of the following is the most appropriate referral for the next step in evaluation?
a. Psychiatry
b. Comprehensive geriatric assessment (CGA)
b. Primary care evaluation
c. Physical therapy