Gastric Cancer: An Overview

Definition:
Gastric cancer, also known as stomach cancer, is a disease in which malignant (cancerous) cells form in the lining of the stomach. It is the fifth most common cancer worldwide and the third leading cause of cancer-related deaths, although its incidence has declined in many countries due to improved hygiene and H. pylori management.

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Types of Gastric Cancer

Most gastric cancers are adenocarcinomas, which arise from the glandular cells lining the stomach. There are two main types of adenocarcinoma:

1. Intestinal type:

   • More common in older adults

   • Often linked to chronic gastritis, H. pylori infection, and dietary factors

   • Tends to grow more slowly and may form gland-like structures

2. Diffuse type:

   • Affects younger people more often

   • Less associated with environmental factors; may have a genetic basis

   • Grows aggressively and infiltrates the stomach wall without forming a clear mass

Other less common types of gastric cancer include:

• Gastrointestinal stromal tumors (GISTs)

• Lymphomas of the stomach

• Carcinoid tumors

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 Risk Factors

Several risk factors increase the likelihood of developing gastric cancer:

Infectious:

• Helicobacter pylori (H. pylori) infection – the most important known risk factor

• Epstein-Barr virus (in rare cases)

Environmental:

• High-salt, smoked, or pickled foods

• Low intake of fruits and vegetables

• Smoking

• Heavy alcohol use

Medical:

• Chronic gastritis (especially atrophic gastritis)

• Pernicious anemia

• Previous gastric surgery (e.g., for ulcers)

• Gastric polyps

• Obesity

Genetic:

• Family history of gastric cancer

• Hereditary diffuse gastric cancer syndrome (mutation in CDH1 gene)

• Lynch syndrome

• Familial adenomatous polyposis (FAP)

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 Symptoms

Early gastric cancer often causes no symptoms, which is why it’s typically diagnosed at a late stage. When present, symptoms may include:

• Indigestion or stomach discomfort

• Bloating after meals

• Loss of appetite

• Nausea or vomiting

• Heartburn

• Weight loss

• Fatigue

• Vomiting blood or black stools (signs of bleeding)

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 Diagnosis

Diagnosing gastric cancer involves a combination of clinical evaluation and imaging:

1. Upper endoscopy (esophagogastroduodenoscopy) – allows direct visualization and biopsy

2. Biopsy – confirms diagnosis by examining tissue for cancer cells

3. Imaging:

   • CT scan (to evaluate spread)

   • Endoscopic ultrasound (for staging)

   • PET scan or laparoscopy (in selected cases)

Laboratory tests may include blood counts, liver function tests, and tumor markers like CEA or CA 19-9, though these are not diagnostic on their own.

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 Staging

Staging determines how far the cancer has spread and is crucial for treatment planning. The TNM staging system is commonly used:

• T: Tumor size and depth of invasion

• N: Lymph node involvement

• M: Metastasis (spread to distant organs)

Stages range from Stage 0 (in situ) to Stage IV (advanced/metastatic cancer).

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 Treatment

Treatment depends on the stage, location, patient health, and cancer type.

1. Surgery (main curative option)

• Subtotal gastrectomy: Removal of part of the stomach

• Total gastrectomy: Complete removal of the stomach

• Lymph node dissection is usually performed at the same time

2. Chemotherapy

• Often used before (neoadjuvant) or after (adjuvant) surgery

• Common regimens: FLOT (fluorouracil, leucovorin, oxaliplatin, docetaxel), ECF, etc.

3. Radiation Therapy

• Occasionally used with chemotherapy, especially in non-resectable tumors

4. Targeted Therapy

• HER2-positive tumors: May respond to trastuzumab

• Other targeted drugs under investigation

5. Immunotherapy

• PD-1 inhibitors (e.g., nivolumab, pembrolizumab) approved for some advanced cases, especially those with MSI-high or PD-L1 positive tumors

6. Palliative Care

• In advanced stages, focus may shift to symptom control and improving quality of life

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 Prognosis

The prognosis depends on the stage at diagnosis:

• Early-stage (localized): 5-year survival rate can be 60–90%

• Advanced/metastatic: 5-year survival drops to <10–20%

Early detection greatly improves outcomes, which is why some countries like Japan and South Korea implement nationwide gastric cancer screening.

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 Prevention

Although not all cases are preventable, steps to reduce risk include:

• Treating H. pylori infection

• Avoiding smoking and excessive alcohol

• Eating a diet rich in fruits and vegetables

• Reducing intake of salted, smoked, and pickled foods

• Genetic counseling and surveillance if at high familial risk

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Summary Table