UPSC-CMS 2021 — Radiology

Question 1: Positron Emission Tomography (PET) used in Preoperative staging of Gastro Oesophageal tumours is to detect

• A. Local spread
• B. Lymph node status
• C. Extension into stomach
• D. Distant metastatic disease (Correct Answer)

Explanation: ***Distant metastatic disease*** - **PET scans** are highly sensitive for detecting metabolically active lesions, making them excellent for identifying **distant metastases** in organs such as the liver, lungs, and bone, which significantly impacts surgical planning. - Identifying **distant metastatic disease** with PET helps in determining if the patient is a candidate for curative surgery or if palliative treatment is more appropriate. *Local spread* - While PET can show increased metabolic activity in the primary tumor, its resolution is often insufficient to precisely delineate the **local extent** of tumor invasion into adjacent tissues, which is better evaluated by **endoscopic ultrasound (EUS)** or **CT scan**. - Assessing local invasion is crucial for determining resectability, but PET's primary role isn't detailed local staging. *Lymph node status* - **PET scans** can detect metabolically active lymph nodes, but they have limitations in differentiating between inflammatory and malignant nodes, especially for very small metastases, leading to potential false positives or negatives. - **Endoscopic ultrasound (EUS)** with fine-needle aspiration (FNA) is generally considered superior for accurate regional **lymph node staging** in gastroesophageal cancer. *Extension into stomach* - The precise **intramural extension** of the tumor within the esophagus and into the stomach is often difficult to determine accurately with PET due to its relatively poor spatial resolution compared to other imaging modalities like **endoscopic ultrasound (EUS)** and **CT**. - **Endoscopic assessment** directly visualizes the tumor and can determine its macroscopic extent into the stomach more precisely than PET.