Stomach cancer (gastric cancer): overview, types, causes, diagnosis and treatment

Causes and risk factors

Multiple environmental, infectious and genetic factors contribute to the development of stomach cancer. Infection with Helicobacter pylori is a major risk factor for non-cardia gastric cancer and is linked to chronic inflammation and a progression from gastritis to atrophy and intestinal-type cancer. Other important influences include tobacco use, certain dietary habits and a family history of gastric cancer.

• Dietary associations: high intake of salted, smoked or pickled foods has been associated with increased risk; fresh fruits and vegetables are generally protective.
• Medical and infectious: longstanding H. pylori infection, pernicious anemia, prior gastric surgery, and certain viruses can raise risk for specific subtypes.
• Genetic factors: inherited syndromes (for example CDH1 mutations) increase risk of hereditary diffuse gastric cancer; other familial clustering is recognized.
• Other: increasing age, male sex, obesity (especially for cancers near the gastroesophageal junction), and smoking.

Types and pathology

The most common form is adenocarcinoma, which arises from the glandular cells lining the stomach. Adenocarcinomas are frequently classified by location (cardia versus non‑cardia) and by histologic patterns such as the Lauren system (intestinal and diffuse types). Other tumours that can involve the stomach include primary lymphomas (including MALT lymphoma), gastrointestinal stromal tumors (GIST), and neuroendocrine (carcinoid) tumours; each has distinct biology and treatment approaches.

Symptoms, diagnosis and staging

Early-stage stomach cancer may produce few or nonspecific symptoms. More advanced disease commonly causes persistent upper abdominal pain, early satiety, unintended weight loss, nausea or vomiting, difficulty swallowing when the tumor is near the cardia, and iron-deficiency anemia from chronic bleeding. Diagnosis relies on endoscopy with biopsy to establish pathology. Imaging such as CT, endoscopic ultrasound and PET may be used to assess local extent and distant spread. Accurate staging guides treatment decisions.

Treatment and prognosis

Treatment depends on stage and tumour type. For localized adenocarcinoma, surgery (partial or total gastrectomy with regional lymph node assessment) offers the best chance of cure and is often combined with perioperative or adjuvant chemotherapy and, in some settings, radiation. Advanced or metastatic disease is managed with systemic chemotherapy, targeted agents for selected molecular profiles (for example HER2-positive tumours), and immunotherapy in appropriate cases. Lymphomas, GISTs and neuroendocrine tumours follow different specialist regimens. Overall outcomes vary substantially by stage at diagnosis and by healthcare context; earlier detection is strongly associated with better prognosis.

Prevention, screening and public health

Reduction of population risk has been linked to improvements in food preservation (refrigeration) and reduced consumption of salted and smoked foods. Eradication of H. pylori infection lowers risk in many settings and is an important preventive measure in high-prevalence populations. Organized screening using endoscopy or other methods is practiced in countries with high incidence (for example parts of East Asia) and can detect cancers at earlier, more treatable stages. Tobacco control, healthier diets and surveillance of high-risk individuals are additional public-health strategies.

For concise background reading see stomach cancer summaries and anatomical references for the stomach. Further specialist information about H. pylori is available at Helicobacter pylori resources.