Gastric Cancer for the PA Exam
Gastric Cancer for the Physician Assistant Licensing Exam
Overview
- Gastric adenocarcinoma is the most common form of gastric cancer, originating from the gastric mucosa. It is subdivided into:
- Intestinal type: Forms glandular structures, often associated with chronic inflammation and environmental factors.
- Diffuse type: Poorly differentiated, lacks gland formation, and includes signet-ring cells.
Epidemiology
- Gastric cancer is more prevalent in East Asia (Japan, South Korea) and Eastern Europe, while incidence is lower in Western countries.
- Higher prevalence in men, usually diagnosed between ages 60–80.
Risk Factors
- Helicobacter pylori infection: The strongest risk factor due to chronic inflammation, gastritis, and progression to intestinal metaplasia.
- Diet: Consumption of smoked, salted, or pickled foods increases the risk.
- Smoking and alcohol: Both increase the risk of gastric cancer.
- Genetic syndromes:
- Hereditary diffuse gastric cancer (HDGC) linked to CDH1 mutations.
- Lynch syndrome and familial adenomatous polyposis (FAP).
- Atrophic gastritis, pernicious anemia, and Epstein-Barr virus infection are also contributing factors.
Pathophysiology
- Gastric cancer typically arises from chronic inflammation progressing through the following steps: gastritis, atrophy, intestinal metaplasia, dysplasia, and eventually adenocarcinoma.
- Intestinal-type adenocarcinoma follows this stepwise progression.
- Diffuse-type is often associated with CDH1 mutations, resulting in a loss of E-cadherin and impaired cell adhesion.
Clinical Presentation
- Early disease is often asymptomatic, leading to delayed diagnosis.
- Nonspecific symptoms:
- Dyspepsia, nausea, and early satiety.
- Weight loss, anorexia, and abdominal pain in later stages.
- Signs of metastatic spread:
- Virchow’s node: Left supraclavicular lymph node enlargement.
- Sister Mary Joseph nodule: Periumbilical mass indicating peritoneal metastasis.
- Krukenberg tumor: Ovarian metastasis in diffuse-type gastric cancer.
Diagnosis
Endoscopy
- Esophagogastroduodenoscopy (EGD) with biopsy is the gold standard for diagnosis and histological confirmation.
- Routine screening is performed in high-risk countries (e.g., Japan, South Korea) for early detection.
Imaging
- CT scan of the chest, abdomen, and pelvis assesses the extent of the disease and checks for metastasis.
- Endoscopic ultrasound (EUS): Helps determine tumor depth and local lymph node involvement.
Tumor Markers
- Carcinoembryonic antigen (CEA) and CA 19-9 may be elevated but are nonspecific and not recommended for screening.
Staging
- The TNM system is used for staging:
- T: Tumor depth and extent of invasion.
- N: Regional lymph node involvement.
- M: Distant metastasis (e.g., liver, peritoneum).
Management
Surgery
- Surgical resection is the only curative treatment.
- Distal gastrectomy: For distal tumors.
- Total gastrectomy: For proximal or diffuse-type cancers.
- D2 lymphadenectomy: Involves removal of regional lymph nodes.
Chemotherapy and Radiation
- Neoadjuvant chemotherapy: Shrinks the tumor before surgery.
- FLOT regimen: 5-FU, leucovorin, oxaliplatin, and docetaxel.
- Adjuvant chemotherapy: Given postoperatively to reduce recurrence risk.
- Chemoradiation: Used in selected cases, especially for locally advanced disease.
Palliative Treatment
- For unresectable or metastatic cases, focus shifts to symptom management and prolonging survival.
- Palliative chemotherapy: Provides survival benefits.
- Palliative radiation: Helps control bleeding or pain.
Prevention
- H. pylori eradication: Reduces the risk of gastric cancer, especially in high-prevalence populations.
- Dietary modification (e.g., increased intake of fresh fruits and vegetables) may lower risk.
Key Points
- Gastric adenocarcinoma is the most common type of gastric cancer, with intestinal and diffuse subtypes.
- H. pylori infection is a major risk factor, alongside dietary habits (smoked/salted foods) and genetic syndromes (e.g., CDH1 mutations).
- Early-stage gastric cancer is often asymptomatic, while advanced disease presents with weight loss, anorexia, and signs of metastasis (e.g., Virchow’s node).
- Diagnosis is made via endoscopy with biopsy, and staging requires CT scans.
- Surgical resection is the primary curative treatment, while chemotherapy and radiation are used in both adjuvant and palliative settings.