A 52-year-old man with a 2-year history of nasal obstruction, chronic purulent nasal discharge, and recurrent episodes of facial pain presents to the ENT clinic. He reports that symptoms persist despite multiple courses of antibiotics and topical nasal corticosteroids. Nasal endoscopy reveals bilateral nasal polyps, edema of the middle turbinates, and thick secretions in the ostiomeatal complex. CT paranasal sinuses shows bilateral maxillary and ethmoid sinus opacification with polypoid changes. He denies asthma, aspirin sensitivity, or cystic fibrosis. What is the most appropriate management at this stage?