Stomach (gastric) cancer arises from the stomach lining and often presents late because early symptoms are subtle. Major risk factors include H. pylori infection, dietary factors, smoking, and inherited mutations such as CDH1. Diagnosis requires endoscopy with biopsy and staging with imaging and endoscopic ultrasound. Treatment is stage-dependent and ranges from endoscopic removal for very early tumors to surgery, chemotherapy, targeted agents, and immunotherapy for advanced disease. Screening programs in high-incidence countries detect cancers earlier and improve outcomes.

What is stomach (gastric) cancer?

Stomach cancer, also called gastric cancer, is a malignant tumor that arises from the lining of the stomach. It can grow locally and spread (metastasize) to nearby organs, lymph nodes, the liver, and occasionally distant sites. Worldwide, most gastric cancers are adenocarcinomas that develop from the stomach's glandular cells.

Risk factors

Several factors increase the chance of developing gastric cancer:

  • Helicobacter pylori infection - one of the strongest and most common risk factors.
  • Diets high in salted, smoked, or preserved foods and low in fresh fruits and vegetables.
  • Tobacco smoking.
  • Older age and male sex.
  • Family history and hereditary syndromes (for example, hereditary diffuse gastric cancer associated with CDH1 mutations).
  • Epstein-Barr virus (EBV) in a subset of tumors.
The relationship between long-term nonsteroidal anti-inflammatory drug (NSAID) use and gastric cancer is complex: NSAIDs can reduce risk in some studies but also increase the risk of gastric ulceration and bleeding.

Symptoms

Early-stage stomach cancer often causes no clear symptoms. When symptoms appear they can be non-specific and include:

  • Indigestion, heartburn, or early fullness after eating.
  • Loss of appetite and unintended weight loss.
  • Upper abdominal discomfort or pain, nausea, or vomiting.
  • Anemia-related fatigue from slow internal bleeding.
Because these symptoms overlap with common benign conditions (ulcers, gastritis, reflux), many cancers are found at an advanced stage unless there is targeted screening or prompt evaluation.

Diagnosis and staging

An upper endoscopy (esophagogastroduodenoscopy) with biopsy is the definitive test to diagnose gastric cancer. Pathology identifies the tumor type and helps guide treatment.

Once confirmed, clinicians stage the cancer to guide therapy. Typical staging tools include contrast CT scans of the chest/abdomen/pelvis, endoscopic ultrasound (to assess depth of invasion and regional lymph nodes), diagnostic laparoscopy in selected cases, and blood tests (including check for anemia). Molecular testing of tumor tissue (HER2, microsatellite instability/MSI, and others) increasingly informs targeted and immune-based treatments.

Treatment overview

Treatment depends on the cancer's stage, location, and molecular features, plus the patient's overall health.

Early-stage

Very early tumors confined to the mucosa or superficial submucosa may be removed endoscopically using endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD). Surgical resection (partial or total gastrectomy) with appropriate lymph node removal remains the standard for localized disease.

Locally advanced and resectable disease

Multimodal therapy - neoadjuvant (preoperative) chemotherapy or chemoradiation followed by surgery, and sometimes adjuvant treatment - improves outcomes compared with surgery alone.

Advanced or metastatic disease

Systemic therapy is the mainstay. Chemotherapy regimens remain central. Targeted agents (for example, trastuzumab for HER2-positive tumors, agents targeting VEGF pathways) and immune checkpoint inhibitors are options for selected patients based on tumor biomarkers. Palliative surgery, radiation, or endoscopic procedures can relieve symptoms.

Follow-up and supportive care, including nutrition support, play key roles across all stages. In countries with high incidence (for example, Japan and South Korea), organized endoscopic screening programs detect many cancers earlier and improve survival outcomes.

FAQs about Stomach Cancer

How is stomach cancer detected?
Definitive detection requires an upper endoscopy with biopsy. Doctors then stage the disease using imaging (CT), endoscopic ultrasound, and sometimes diagnostic laparoscopy.
Can stomach cancer be prevented?
Reducing modifiable risks helps: treat Helicobacter pylori infections, avoid tobacco, limit heavily salted and smoked foods, and eat more fruits and vegetables. Genetic counseling is advised for families with hereditary diffuse gastric cancer (CDH1).
What are treatment options for early-stage gastric cancer?
Very early tumors may be treated with endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD). More advanced localized tumors typically require surgical resection with lymph node removal, often combined with chemotherapy or chemoradiation.
Are there targeted or immune therapies for advanced stomach cancer?
Yes. Targeted drugs (for example, trastuzumab for HER2-positive tumors) and immune checkpoint inhibitors are used in selected patients based on tumor markers such as HER2 status and MSI.
When should I see a doctor about stomach symptoms?
Consult a healthcare provider for persistent or progressive symptoms such as unexplained weight loss, persistent upper abdominal pain, difficulty swallowing, persistent vomiting, or signs of anemia (fatigue, pale skin). Early evaluation improves the chance of curative treatment.