**Core Concept**
The management of carcinoma of the lower 1/3 of the oesophagus involves a multidisciplinary approach, including chemo-radiotherapy, which can induce a complete response in symptoms like dysphagia. However, this does not necessarily mean that the tumour has been completely eradicated, and further treatment may be required to prevent recurrence and improve survival.

**Why the Correct Answer is Right**
A complete response to chemo-radiotherapy in a patient with carcinoma of the lower 1/3 of the oesophagus suggests that the tumour has been significantly reduced in size or has been eliminated. However, microscopic residual disease may still be present, which can lead to recurrence. Esophagectomy, or surgical removal of the oesophagus, is often recommended in such cases to remove any remaining tumour cells and prevent recurrence. This is particularly important in early-stage cancers, where the risk of recurrence is higher.

**Why Each Wrong Option is Incorrect**
**Option A:** Reassuring the patient without further investigation or treatment is not appropriate, as it does not address the underlying risk of recurrence.
**Option B:** Following the patient with CT scans every 6 months may not be sufficient to detect early recurrence, and does not address the risk of microscopic residual disease.
**Option D:** EUS (Endoscopic Ultrasonography) may be useful for staging and detecting residual disease, but it is not the next step in management, and does not address the need for surgical removal of the tumour.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that a complete response to chemo-radiotherapy does not necessarily mean that the tumour has been completely eradicated, and further treatment may be required to prevent recurrence and improve survival.

**✓ Correct Answer: C. Esophagectomy**