**Core Concept**
The treatment of choice for a large antrochoanal polyp is aimed at removing the polyp and addressing the underlying anatomical and physiological factors contributing to its growth. This typically involves a surgical approach to ensure complete removal and prevent recurrence.

**Why the Correct Answer is Right**
The current treatment of choice for a large antrochoanal polyp is endoscopic sinus surgery (ESS). ESS allows for the removal of the polyp while preserving the surrounding nasal and sinus anatomy. This approach enables the surgeon to address the underlying mucosal disease and remove the polyp in its entirety, reducing the risk of recurrence. During ESS, the surgeon uses a nasal endoscope to visualize the polyp and surrounding structures, and then uses specialized instruments to remove the polyp and restore normal sinus drainage.

**Why Each Wrong Option is Incorrect**
**Option A:** Antibiotic therapy alone is not sufficient to treat an antrochoanal polyp, as the polyp's growth is driven by underlying anatomical and physiological factors, not solely by bacterial infection.
**Option B:** Functional endoscopic nasal surgery (FESS) is a type of endoscopic sinus surgery, but the term is often used to describe a broader range of procedures, including those not specifically aimed at removing polyps.
**Option C:** Polypectomy via a Caldwell-Luc procedure is an older surgical approach that involves making an incision in the upper gum to access the maxillary sinus. While this approach can be effective, it is generally considered less desirable than ESS due to its more invasive nature and increased risk of complications.

**Clinical Pearl / High-Yield Fact**
It's essential to distinguish between antrochoanal polyps and other types of nasal polyps, such as those associated with chronic rhinosinusitis or allergic fungal rhinosinusitis. The treatment approach may differ depending on the underlying cause of the polyp.

**Correct Answer:** C.