iSymptom

ConditionCancer

Stomach Cancer (Gastric Cancer)

Stomach cancer, or gastric cancer, is cancer that starts in the lining of the stomach, most often as an adenocarcinoma. Early stomach cancer usually causes no symptoms or only vague ones such as indigestion, feeling full quickly, or mild upper belly discomfort, so it is often found late. Warning signs include unexplained weight loss, difficulty swallowing, persistent vomiting, black stools and anemia. H. pylori infection is the main preventable cause. Treatment combines surgery and chemotherapy, and early cancers can be cured.

Also called: Gastric cancer, gastric adenocarcinoma, stomach adenocarcinoma

By the iSymptom editorial team · Updated · 4 min read

At a glance

What it is
Cancer of the stomach lining, mostly adenocarcinoma; lymphomas and GIST are rarer types.
Who gets it
Mostly people over 60; more common in men and in people of East Asian, Hispanic, Black and Native American descent.
Early symptoms
Often none, or indigestion, early fullness, mild upper abdominal pain.
Red flags
Weight loss, trouble swallowing, persistent vomiting, black stools, anemia, an abdominal lump.
Diagnosis
Upper endoscopy with biopsy, CT staging.
Treatment
Endoscopic removal for very early cancer; surgery plus chemotherapy; targeted and immunotherapy for advanced disease.

When to get help

Call 911 or go to the ER

  • Vomiting blood or coffee-ground material, or black, tarry stools with dizziness or fainting
  • Persistent vomiting with inability to keep anything down, especially with a swollen upper belly

See a doctor within a day or two

  • Unexplained weight loss with indigestion or upper abdominal pain
  • Food sticking when swallowing, or getting worse over weeks
  • Iron deficiency anemia without an obvious cause
  • New indigestion that does not settle, especially over age 55

Book a routine appointment

  • Indigestion or heartburn lasting more than 3 to 4 weeks despite treatment
  • A family history of stomach cancer, or known H. pylori infection that has not been treated
  • Long-standing atrophic gastritis or pernicious anemia, for surveillance advice

How stomach cancer develops

Most stomach cancers develop slowly over many years. Long-term inflammation of the stomach lining, usually from H. pylori, leads to chronic gastritis, then thinning of the lining (atrophy), intestinal metaplasia, dysplasia and finally cancer. Some cancers, particularly the "diffuse" type, spread through the stomach wall rather than forming a visible lump, and can be harder to spot.

Cancers at the junction of the esophagus and stomach behave somewhat differently and are linked to acid reflux and obesity.

Symptoms

Early stomach cancer

  • indigestion or heartburn
  • feeling full after eating only a little (early satiety)
  • mild upper abdominal discomfort or bloating
  • nausea
  • loss of appetite

These are common and usually caused by harmless conditions, but persistence or combination with red flags needs assessment.

Later symptoms

  • unexplained weight loss
  • difficulty swallowing, if the cancer is near the top of the stomach
  • vomiting, sometimes with blood, if the outlet is blocked
  • black stools or anemia from bleeding, causing tiredness and breathlessness
  • a lump or swelling in the upper abdomen
  • swelling of the abdomen from fluid (ascites)
  • a lump above the left collarbone (enlarged lymph node)
  • yellowing of the skin and eyes if it spreads to the liver

Risk factors

  • Helicobacter pylori infection: the leading cause
  • age over 60 and male sex
  • smoking
  • diets high in salt, salted, smoked or pickled foods, and low in fruit and vegetables
  • family history of stomach cancer
  • inherited syndromes: hereditary diffuse gastric cancer (CDH1 gene), Lynch syndrome, familial adenomatous polyposis, BRCA2
  • pernicious anemia and atrophic gastritis
  • previous stomach surgery
  • obesity and reflux (for cancers at the junction with the esophagus)
  • Epstein-Barr virus (a subset)

Diagnosis

  1. Upper endoscopy (gastroscopy): a camera passed through the mouth to examine the stomach and take biopsies. This is the key test.
  2. Biopsy testing: confirms cancer and checks markers such as HER2, PD-L1, MSI and claudin 18.2, which guide treatment.
  3. CT scan of the chest, abdomen and pelvis to stage the cancer.
  4. Endoscopic ultrasound to assess depth and nearby lymph nodes.
  5. PET-CT in some cases.
  6. Laparoscopy to look for spread to the abdominal lining before major surgery.
  7. Blood tests: blood count for anemia, liver function.

Stages

Stomach cancer is staged from I (confined to the inner layers) to IV (spread to distant organs). Stage determines treatment and outlook.

Treatment

  • Endoscopic resection: very early cancers confined to the lining can be removed during endoscopy.
  • Surgery: partial or total gastrectomy with removal of nearby lymph nodes; the main curative treatment for localized cancer.
  • Perioperative chemotherapy: given before and after surgery, commonly the FLOT regimen, improves survival.
  • Radiotherapy: in selected cases, often with chemotherapy.
  • Advanced cancer: chemotherapy combined with targeted therapy (trastuzumab for HER2-positive, zolbetuximab for claudin 18.2-positive) or immunotherapy (nivolumab or pembrolizumab), depending on tumor markers.
  • Supportive care: nutrition support, treating anemia, stents for blockage, pain control and palliative care.

Life after gastrectomy

People often need smaller, more frequent meals, vitamin B12 injections, and iron and calcium monitoring. "Dumping syndrome," with sweating, dizziness and diarrhea after meals, can occur and improves with diet changes.

Outlook

In the US, about a third of people with stomach cancer survive 5 years overall. When found while still localized, survival is much higher, around 75%. Early detection and treatment of H. pylori make a significant difference.

Prevention

  • test for and treat H. pylori infection, especially with a family history of stomach cancer
  • do not smoke
  • eat plenty of fruit and vegetables; limit salt and processed meats
  • genetic counseling for families with hereditary syndromes
  • surveillance endoscopy for some people with precancerous changes

Frequently asked questions

What are the early signs of stomach cancer?

Early stomach cancer often causes no symptoms. When it does, they are vague: indigestion, heartburn, feeling full quickly, mild upper belly discomfort, nausea and reduced appetite. Persistent symptoms, especially with weight loss or anemia, need an endoscopy.

What causes stomach cancer?

The most important cause is long-term infection with H. pylori bacteria. Other risk factors include smoking, a diet high in salty and smoked foods, older age, family history, inherited syndromes and chronic atrophic gastritis.

Can H. pylori cause stomach cancer?

Yes. Long-term H. pylori infection causes chronic inflammation that can lead to stomach cancer over many years. Most infected people never develop cancer, but treating the infection lowers the risk.

What is the survival rate for stomach cancer?

Overall 5-year survival in the US is about 36%. If the cancer is found before it has spread beyond the stomach, survival is around 75%. Outcomes are much better when cancer is found early.

Sources

This guide was written from current patient and clinical guidance, including:

  • American Cancer Society: Stomach cancer; Key statistics for stomach cancer
  • National Cancer Institute: Gastric cancer treatment (PDQ)
  • NCCN Guidelines for Patients: Stomach cancer
  • American College of Gastroenterology: Clinical guideline: Treatment of Helicobacter pylori infection (2024)
  • MedlinePlus: Stomach cancer
  • NHS: Stomach cancer