USMLE Guide: Stomach Cancer

Introduction

Stomach cancer, also known as gastric cancer, is a malignant tumor that arises from the lining of the stomach. It is a significant global health issue and is the fifth most common cancer worldwide. This guide aims to provide a comprehensive overview of stomach cancer, including its epidemiology, etiology, clinical features, diagnosis, and management.

Epidemiology

Stomach cancer is more prevalent in certain regions, including East Asia, Eastern Europe, and parts of South America. It is more common in males and typically affects individuals over the age of 55. Several risk factors contribute to the development of stomach cancer, such as:

• Helicobacter pylori infection: Chronic infection with this bacterium is the most significant risk factor for stomach cancer.
• Dietary factors: A diet rich in smoked, salted, or pickled foods, and low in fruits and vegetables, increases the risk.
• Tobacco and alcohol use: Both tobacco smoking and excessive alcohol consumption are associated with an increased risk of stomach cancer.
• Family history: Individuals with first-degree relatives who have had stomach cancer are at a higher risk.

Etiology

The development of stomach cancer involves a multifactorial process. The main etiological factors are:

1. Helicobacter pylori infection: This bacterium colonizes the gastric mucosa, leading to chronic inflammation and subsequent carcinogenesis.
2. Genetic predisposition: Certain genetic mutations and polymorphisms, such as E-cadherin gene (CDH1) mutations, increase the risk of stomach cancer.
3. Environmental factors: Exposure to certain chemicals like asbestos and coal dust, as well as radiation, may contribute to the development of stomach cancer.

Clinical Features

The clinical presentation of stomach cancer can vary, and early-stage disease may be asymptomatic. However, common clinical features include:

• Epigastric pain: Persistent or recurrent pain in the upper abdomen is a common symptom.
• Dyspepsia: Chronic indigestion, bloating, and early satiety are often reported.
• Weight loss: Unexplained weight loss is a typical manifestation of advanced disease.
• Gastrointestinal bleeding: This can lead to anemia, melena (black, tarry stools), or hematemesis (vomiting blood).

Diagnosis

Diagnosing stomach cancer involves a combination of clinical evaluation, imaging studies, and histopathological examination. The following diagnostic approaches are commonly utilized:

1. Upper endoscopy: This allows direct visualization of the stomach lining and enables targeted biopsies.
2. Imaging studies: Computed tomography (CT) scans and endoscopic ultrasound (EUS) help determine the extent of the disease and identify lymph node involvement.
3. Biopsy and histopathology: Tissue samples obtained via endoscopy are examined histologically to confirm the diagnosis and identify the tumor type.

Management

The management of stomach cancer depends on various factors, such as the stage of the disease, patient's overall health, and patient preferences. Common treatment modalities include:

1. Surgical resection: Surgery is the mainstay of treatment for localized disease and involves removing the tumor along with nearby lymph nodes.
2. Chemotherapy: Neoadjuvant or adjuvant chemotherapy is often administered to shrink the tumor before surgery or kill any remaining cancer cells after surgery.
3. Radiation therapy: Radiation may be used in combination with surgery and chemotherapy to improve local control.
4. Targeted therapies: Certain targeted drugs, such as trastuzumab and ramucirumab, are used in specific cases based on tumor characteristics.

Prognosis

The prognosis of stomach cancer depends on the stage at diagnosis, with earlier stages having a more favorable outcome. Unfortunately, many cases are diagnosed at advanced stages, leading to a poorer prognosis. Regular follow-up and surveillance are essential to monitor for recurrence and manage any treatment-related complications.

In conclusion, stomach cancer is a significant health concern globally. Understanding its epidemiology, etiology, clinical features, diagnosis, and management is crucial for medical professionals. By staying informed and applying evidence-based practices, physicians can contribute to better patient outcomes and reduce the burden of this disease.