Esophageal Cancer for the USMLE Step 3 Exam
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Esophageal Cancer for USMLE Step 3
Definition
- Esophageal Cancer: A malignant tumor originating in the esophagus, classified into two primary types:
- Squamous Cell Carcinoma (SCC): Arises from the squamous cells lining the esophagus, most common globally.
- Adenocarcinoma: Develops from the columnar epithelium, often in the context of Barrett’s esophagus, and is more common in Western countries.
Epidemiology
- Squamous Cell Carcinoma (SCC):
- Predominates in developing regions such as Asia and Africa, affecting the upper and middle esophagus.
- Adenocarcinoma:
- Common in the U.S. and Europe, primarily affecting the lower esophagus near the gastroesophageal junction.
- Strongly associated with GERD and Barrett’s esophagus.
Risk Factors
- Squamous Cell Carcinoma:
- Tobacco and alcohol use: Major contributors.
- Diet: Low intake of fruits and vegetables; consumption of hot beverages.
- Achalasia: Increased risk due to prolonged stasis of food.
- Caustic injury: Prior injury from ingestion of caustic substances.
- Adenocarcinoma:
- GERD and Barrett’s Esophagus: Chronic acid reflux is the primary risk factor.
- Obesity: Increases intra-abdominal pressure, promoting reflux and Barrett’s esophagus.
- Smoking: Contributes to both adenocarcinoma and SCC risk.
Pathophysiology
- Squamous Cell Carcinoma:
- Chronic irritation from smoking, alcohol, or dietary factors leads to dysplasia of the squamous epithelium, progressing to carcinoma.
- Typically occurs in the upper or middle esophagus.
- Adenocarcinoma:
- Develops from Barrett’s esophagus, a condition in which chronic GERD causes metaplasia of the normal squamous epithelium into columnar epithelium with goblet cells.
- Primarily occurs in the distal esophagus.
Clinical Features
- Dysphagia: The most common symptom, initially with solids and later progressing to liquids as the tumor obstructs the esophagus.
- Weight Loss: Due to difficulty swallowing and cancer-associated cachexia.
- Odynophagia: Pain with swallowing, often indicating advanced disease.
- Chest Pain: Substernal pain or discomfort, possibly indicating tumor invasion.
- Hoarseness: Due to recurrent laryngeal nerve involvement, suggesting advanced disease.
- GI Bleeding: Hematemesis or melena may occur from tumor ulceration.
Diagnosis
- Endoscopy with Biopsy:
- Esophagogastroduodenoscopy (EGD): Gold standard for diagnosing esophageal cancer. It allows direct visualization and biopsy of the tumor to confirm squamous cell carcinoma or adenocarcinoma.
- Barium Swallow:
- May reveal a stricture or apple-core lesion, suggestive of esophageal cancer.
- Imaging:
- CT or PET/CT scans: Essential for staging to assess local invasion and distant metastasis (commonly to the liver, lungs, or lymph nodes).
Staging
- TNM Classification:
- T (Tumor): Assesses depth of invasion into the esophageal wall and surrounding tissues.
- N (Nodes): Indicates regional lymph node involvement.
- M (Metastasis): Indicates presence of distant metastasis to organs such as the liver or lungs.
Treatment
- Surgical Resection:
- Esophagectomy: The main treatment for localized disease without distant metastasis. May involve removing part or all of the esophagus and reconstructing it using a portion of the stomach or colon.
- Endoscopic Mucosal Resection (EMR):
- Used for early-stage tumors (T1a) confined to the mucosa.
- Neoadjuvant Chemoradiotherapy:
- Preoperative chemoradiation is standard for locally advanced tumors (T2 or higher), improving surgical outcomes by shrinking the tumor.
- Palliative Therapy:
- For advanced or metastatic disease, treatment is aimed at relieving symptoms such as dysphagia and pain.
- Esophageal stenting: Helps to relieve obstruction and improve swallowing.
- Palliative Chemoradiotherapy: Can control symptoms and slow disease progression in metastatic cases.
Complications
- Local Invasion: Tumor invasion of nearby structures (e.g., trachea) may cause tracheoesophageal fistulas.
- Distant Metastasis: Common sites include the liver, lungs, and adrenal glands.
- Malnutrition: Secondary to dysphagia and decreased oral intake.
Prevention
- Tobacco and Alcohol Cessation: Reduces the risk of squamous cell carcinoma.
- GERD Management: Treating GERD and performing surveillance in patients with Barrett’s esophagus can reduce the risk of adenocarcinoma.
- Dietary Measures: A diet rich in fruits and vegetables may help reduce the risk of esophageal cancer.
Key Points
- Esophageal cancer is categorized into squamous cell carcinoma (more common globally) and adenocarcinoma (linked to GERD and Barrett’s esophagus, common in Western countries).
- Major risk factors for SCC include smoking, alcohol, and hot beverages, while GERD and Barrett’s esophagus are primary contributors to adenocarcinoma.
- Dysphagia, weight loss, chest pain, and GI bleeding are common symptoms. Diagnosis is confirmed via endoscopy and biopsy.
- Treatment for localized disease includes esophagectomy, while neoadjuvant chemoradiotherapy is used for locally advanced tumors. Palliative care is provided for metastatic disease.
- Prevention strategies focus on managing GERD, avoiding tobacco and alcohol, and improving dietary habits to reduce cancer risk.