The short answer
Being told you have stomach cancer is overwhelming, and it is normal to feel that way. In the first days, your team confirms the details and stage, explains options like surgery, chemotherapy, radiation, targeted therapy, and immunotherapy, and helps you make a plan. You do not have to decide everything at once, and asking questions is encouraged.
A stomach cancer diagnosis is a lot to take in — it is normal to feel shocked or scared.
Early on, your team confirms the type and stage before recommending treatment.
A medical oncologist and a surgeon usually leads care, working with a wider team.
Common treatment options include surgery, chemotherapy, radiation, targeted therapy, and immunotherapy.
Choose how you want to understand this
The full explanation.
Find the histology line on your report
Stomach cancer is not one disease. The National Cancer Institute splits adenocarcinoma into two main patterns, and they behave differently.
Intestinal type. Well differentiated, forming tubular and glandular structures that still look organized under the microscope.
Diffuse type. Undifferentiated or poorly differentiated, with no gland formation. NCI notes this type can spread through the stomach wall and produce linitis plastica, a stiff, thickened stomach that no longer expands.
Some tumors show mixed features. Ask which pattern your report describes, because the diffuse type changes both surgical planning and expectations.
Biomarkers to confirm before first-line treatment
This is the item most likely to be missed in the first two weeks.
HER2 status has to be known. So does CLDN18.2, a protein called claudin 18.2 that sits on some stomach cancer cells.
The reason is a specific FDA approval. Zolbetuximab-clzb is approved for first-line treatment of adults with locally advanced unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma that is HER2-negative and CLDN18.2 positive. Positivity is determined by a companion test, the VENTANA CLDN18 (43-14A) RxDx Assay.
Note how the two markers interact. A HER2-positive tumor does not qualify for that drug. A tumor never tested for CLDN18.2 cannot qualify either.
Ask directly: has my tumor been tested for HER2 and for CLDN18.2, and when do the results come back?
Risk factors, including one that is treatable
NCI lists Helicobacter pylori infection of the stomach first among risk factors. Others include older age, male sex, a diet low in fruits and vegetables and high in salted or smoked foods, chronic atrophic gastritis, intestinal metaplasia, pernicious anemia, adenomatous polyps, family history, cigarette smoking, Ménétrier disease, Epstein-Barr virus infection, and inherited syndromes.
H. pylori matters because it can be tested for and treated. Ask whether you have been tested. Ask whether close relatives should be.
Where the numbers sit
NCI's SEER program gives 5-year relative survival for stomach cancer, using cases from 2016 to 2022:
- Localized — 78.1%.
- Regional — 39.0%.
- Distant — 8.1%.
The stage distribution explains the overall figure of 39.8%. Only 32% are found localized, while 35% are already distant. For 2026 the American Cancer Society projects 31,510 new cases and 10,740 deaths, the figures SEER carries. Most diagnoses fall between ages 65 and 74.
These are group averages across many years and older treatments. They are not a forecast for you.
Very early disease is sometimes handled through the endoscope
For stage 0 disease, NCI reports over 90% 5-year survival with surgery. It also describes endoscopic mucosal resection as an option for selected patients with good-risk features.
Those features are specific: Tis or T1a depth, a diameter of 2 cm or less, and a predominantly differentiated type. If a doctor offers an endoscopic approach, ask whether your tumor meets all three.
Stages II and III: drugs before surgery, not only after
This is a real change from how stomach cancer used to be treated, and it is worth understanding.
FLOT. Docetaxel, oxaliplatin, and fluorouracil with leucovorin, given before and after surgery. NCI reports the AIO-FLOT4 trial: median overall survival was 50 months with FLOT against 35 months with ECF or ECX, with a hazard ratio of 0.77.
CLASSIC. Capecitabine with oxaliplatin after surgery raised 3-year disease-free survival to 74% from 59%.
SWOG-9008. Adjuvant chemoradiation gave a median survival of 35 months against 27 months.
Surgery is a gastrectomy, meaning removal of part or all of the stomach, together with removal of regional lymph nodes.
If someone proposes going straight to surgery for stage II or III disease, ask why chemotherapy is not being given first.
One blood test that can prevent a severe reaction
Fluorouracil and capecitabine are both fluoropyrimidines. Some people cannot break them down normally.
NCI states that an estimated 1% to 2% of the population carries germline pathogenic variants in DPYD, the gene for the enzyme that clears these drugs. Testing costs less than $200. NCI also notes it may delay therapy by about 2 weeks.
That trade-off is worth discussing out loud, because nearly every regimen above contains a fluoropyrimidine.
Advanced disease that is HER2-negative and CLDN18.2 positive
Two trials support zolbetuximab, and the numbers are modest but real.
SPOTLIGHT enrolled 565 patients, comparing zolbetuximab plus mFOLFOX6 against placebo plus mFOLFOX6. Median progression-free survival was 10.6 months against 8.7. Median overall survival was 18.2 months against 15.5.
GLOW enrolled 507 patients, using CAPOX as the chemotherapy backbone. Median progression-free survival was 8.2 months against 6.8. Median overall survival was 14.4 months against 12.2.
It starts with a larger loading infusion into a vein, then continues either every 3 weeks or every 2 weeks. The amounts are worked out from your body size by the team giving it.
The FDA lists these among the serious adverse reactions occurring in 2% or more: vomiting, nausea, neutropenia, diarrhea, decreased appetite, pneumonia, and pulmonary embolism. Nausea and vomiting are common enough with this drug to be planned for in advance, not managed after the fact.
Get help now
Go to an emergency department for:
- Vomiting blood, or material that looks like coffee grounds.
- Black, tarry stools.
- Severe abdominal pain that comes on suddenly.
- Chest pain or sudden shortness of breath.
- Being unable to keep any fluids down for 24 hours.
Call the oncology team the same day for:
- A temperature of 100.4 °F (38 °C) or higher during chemotherapy, the threshold CDC gives.
- Vomiting that stops you taking your oral medicines.
- New swelling or pain in one leg.
Questions for the first appointment
- Is my tumor intestinal type or diffuse type?
- Have HER2 and CLDN18.2 been tested, and when will results arrive?
- Have I been tested for H. pylori?
- Is chemotherapy planned before surgery, and which regimen?
- Will I be tested for DPYD variants before fluorouracil or capecitabine?
- How much of my stomach would surgery remove, and when do I meet a dietitian?
Stomach cancer, in more depth
Stomach Cancer is the full overview. Stomach Cancer Treatment goes deeper on the options above. Stomach Cancer Symptoms covers what led here.
Sources
- NCI PDQ — Gastric Cancer Treatment (Health Professional Version)
- NCI SEER — Cancer Stat Facts: Stomach Cancer
- U.S. Food and Drug Administration — FDA approves zolbetuximab-clzb with chemotherapy for gastric or gastroesophageal junction adenocarcinoma
- National Cancer Institute — Infection and Neutropenia during Cancer Treatment
Words to know
Tap any term to see what it means.
Common questions
I was just diagnosed with stomach cancer — what should I do first?
Take a breath. In the first days, your team confirms the type and stage and explains your options. You usually do not need to decide anything immediately, so gather information, bring support to appointments, and write down your questions.
How is the stage worked out?
This usually involves an endoscopy with a biopsy, imaging to work out the stage, and tumor tests (such as HER2) that can guide treatment. The stage describes how far the cancer has spread and helps your team recommend the right treatment.
What treatments are used for stomach cancer?
Common options include surgery, chemotherapy, radiation, targeted therapy, and immunotherapy. Which are right for you depends on the type, stage, and your overall health — your team will explain the choices.
Can I get a second opinion?
Yes. Getting a second opinion is common and reasonable, especially before major decisions. It will not offend your team, and many doctors encourage it.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Your next step
Build a personal list of questions and things to bring.
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Get urgent help
Immediate emergency guidance for fever (>100.4°F during chemo), severe pain, or shortness of breath.
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Sources last checked: 2026-08-16 what this meansLast updated: 2026-08-20Next planned review: 2027-07-12
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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