The short answer
Where the tumor sits changes the outlook: NCI says more than half of localized lower stomach cancers can be cured, while proximal gastric cancer has a 5-year survival rate of only 10% to 15%. For advanced disease, four biomarkers steer the first choice.
Site matters. More than half of people with localized cancer in the lower stomach can be cured, but proximal gastric cancer carries a 5-year survival rate of only 10% to 15%.
Early-stage disease is only 10% to 20% of United States diagnoses, so most people are found after the cancer has reached regional or distant sites.
Four biomarkers steer advanced treatment: HER2, PD-L1 combined positive score, CLDN18.2, and mismatch repair or microsatellite status.
A D2 gastrectomy removes a defined wider field of nodes and is the standard used in the trials guiding chemotherapy after surgery, so it shapes how your results get read later.
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The full explanation.
Start with where the tumor sits
Stomach cancer is not one situation. Where the tumor sits inside the stomach changes the outlook enough that it belongs in your first conversation.
NCI's clinical summary is direct about it. More than half of people with localized cancer in the lower stomach can be cured. But for proximal gastric cancer, high in the stomach, the 5-year survival rate is only 10% to 15%. That holds even when the disease looks localized.
Timing is the other hard fact. Early-stage disease makes up only 10% to 20% of United States diagnoses. Most people are found with cancer that has already reached regional or distant sites.
So the first two questions are simple:
- Where exactly in the stomach is the tumor?
- Has it spread to lymph nodes or beyond, and what test showed that?
The four biomarkers that change the plan
For advanced or spreading stomach cancer, four test results steer treatment. Ask which ones have been run on your tumor. Ask what each one showed. Our page on biomarker testing explains how the tests are done.
HER2. In the trial that set the standard, a tumor counted as HER2-positive if staining scored 3+ on IHC, or if a FISH test showed a HER2 to CEP17 ratio of 2 or more. In the ToGA trial, 3,665 tumors were tested and 810 were positive, about 22%. Adding trastuzumab to chemotherapy raised median survival from 11.1 months to 13.8 months.
PD-L1 combined positive score. In CheckMate-649, 1,581 people got chemotherapy with or without nivolumab. Median survival was 14.0 months with nivolumab and 11.3 months without. In the group scoring 5 or higher, it was 14.4 months versus 11.1 months.
CLDN18.2. This one is newer. Two trials added zolbetuximab to chemotherapy in CLDN18.2-positive, HER2-negative disease. GLOW enrolled 507 people on CAPOX. Median survival was 14.39 months with zolbetuximab and 12.16 months with placebo. SPOTLIGHT enrolled 565 people on mFOLFOX6. Median progression-free survival was 10.61 months versus 8.67 months.
Mismatch repair or microsatellite status. Ask whether this was checked. It can open immunotherapy options.
The operation, and the lymph nodes
For cancer that can be removed, surgery is the centerpiece. Two things are worth pinning down.
The first is how much stomach comes out. That depends on where the tumor sits and how far it has spread along the stomach wall.
The second is the lymph node dissection. A D2 gastrectomy removes a defined wider field of nodes. It is the standard used in the trials that guide chemotherapy after surgery. So it shapes how your results get read later.
Worth asking:
- How much of my stomach will be removed, and what will eating be like afterward?
- Will this be a D2 lymph node dissection?
- How many operations like mine does this surgeon do each year?
Chemotherapy around surgery
Three trials set the current options. They do not all point the same way.
FLOT4 enrolled 716 people with stage IB to III removable gastric or gastroesophageal adenocarcinoma. One group got FLOT. That is docetaxel, oxaliplatin, and fluorouracil with leucovorin, given in a set number of cycles before surgery and the same number after. The other group got the older ECF/ECX regimen. Median survival was 50 months with FLOT and 35 months with ECF/ECX. Margin-free removal reached 85% versus 78%.
Side effects differed rather than being simply worse. Hospitalization rates were close: 25% for FLOT and 26% for ECF/ECX. FLOT brought more severe infection, low white cells, diarrhea, and nerve damage. ECF/ECX brought more nausea, blood clots, and anemia.
MAGIC tested ECF chemotherapy before and after surgery, against surgery alone. The 5-year survival rate was 36.3% with chemotherapy and 23% without.
CLASSIC took a different route. It enrolled 1,035 people in South Korea, China, and Taiwan who had already had a curative D2 gastrectomy. Capecitabine plus oxaliplatin followed for about six months. Three-year disease-free survival rose from 59% to 74%.
One trial is useful for what it did not find. CALGB-80101 tested heavier chemotherapy with radiation in 546 people after curative removal. The 5-year survival rate was 44% in both arms.
Worth asking:
- Are we giving chemotherapy before surgery, after it, or both?
- Which regimen, and why that one for me?
- What is the plan if I cannot finish the cycles that come after surgery?
When the cancer has spread
For metastatic disease, the biomarker results above drive the first choice. A few specifics are worth naming.
Trastuzumab can be paired with pembrolizumab and chemotherapy for HER2-positive metastatic disease. In KEYNOTE-811, with 434 patients, the response rate at the first analysis was 74.4% with pembrolizumab added. It was 51.9% without. For people who cannot tolerate pembrolizumab, trastuzumab can be given with cisplatin and fluorouracil, or with capecitabine.
Pembrolizumab with chemotherapy has not beaten chemotherapy alone across the board. KEYNOTE-062 enrolled 763 patients. Neither pembrolizumab alone nor pembrolizumab with chemotherapy proved superior. In the subgroup scoring 10 or higher, pembrolizumab alone gave a median survival of 17.4 months against 10.8 months for chemotherapy. But the trial's statistical plan did not test that difference further. That distinction matters if the number gets quoted to you as a result.
What a second opinion is actually for
A second opinion helps most when a specific choice is genuinely open. In stomach cancer, three moments qualify.
The first is the extent of surgery, especially when a total gastrectomy is on the table. The second is the choice of chemotherapy regimen and its timing around the operation. The third is whether biomarker testing is complete before a first-line drug is picked.
Ask whether your case has gone to a tumor board. Ask whether a clinical trial would need to start before any treatment does, because some eligibility windows close once therapy begins.
Living with the plan
Two practical threads run under all of this.
Eating. Stomach surgery changes how much you can eat at once. It changes how fast food moves, and how well you absorb vitamin B12 and iron. Ask who manages that. Ask when nutrition support starts, not whether it will.
Symptom control alongside treatment. Palliative care runs in parallel with cancer treatment, not after it. Asking for a referral at the start is reasonable.
For the disease overview and how stage is assigned, see stomach cancer and cancer staging.
Sources
- National Cancer Institute, Gastric Cancer Treatment PDQ, health professional version, updated February 21, 2025; accessed August 6, 2026
Words to know
Tap any term to see what it means.
Common questions
Which biomarker tests should be run before treatment starts?
Ask about HER2, PD-L1 combined positive score, CLDN18.2, and mismatch repair or microsatellite status. Each opens a different option, and some trial eligibility windows close once therapy begins.
What is a D2 gastrectomy?
An operation that removes a defined wider field of lymph nodes along with the stomach. It was the surgery used in trials such as CLASSIC, which is why it affects how later results are read.
Is chemotherapy given before surgery or after it?
Both patterns are standard. FLOT4 split chemotherapy evenly before and after surgery; CLASSIC gave it only afterwards. Which one suits you depends on where the tumour sits, its stage, your fitness and organ function, and your team sets the drugs, the number of cycles and the interval. Ask which pattern they plan, and what happens if you cannot finish the part that comes after.
Will I be able to eat normally afterwards?
Stomach surgery changes how much you can eat at once, how fast food moves, and how well you absorb vitamin B12 and iron. Ask who manages that, and when nutrition support starts.
Questions to ask your doctor
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Sources last checked: 2026-08-06 what this meansLast updated: 2026-08-19Next planned review: 2027-07-30
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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: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
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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