A 42-year-old woman with a 3-month history of bilateral nasal polyps presents after 6 weeks of topical fluticasone nasal spray (200 µg twice daily). She reports minimal improvement in nasal obstruction and continues to have sleep disturbance. Nasal endoscopy confirms persistent large polyps bilaterally. She denies asthma, cough, or recurrent infections. Chest X-ray is normal. What is the most appropriate next step in management?