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Cancer types

Stomach Cancer

Stomach cancer is most often adenocarcinoma, and HER2, PD-L1, MSI/MMR, and CLDN18.2 status can affect which treatment options are discussed.

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Ilustrasi editorial lambung dan sambungan esofagus dengan area tumor
HER2PD-L1MSI / MMRCLDN18.2

Not a diagnosis and not final medical advice. Must be reviewed by a doctor.

What is most important to know?

Gastric cancer develops in the inner lining of the stomach wall and often only causes symptoms at an advanced stage.

Most are adenocarcinomas, with intestinal and diffuse types that have different behavior.

Endoscopic examination with biopsy is the basis for diagnosis, followed by imaging to determine the stage.

Gastric cancer is a cancer with a high incidence rate in Asia. Specific figures per country are not shown because they need to be quoted directly from the source.

Biomarker results can change the discussion.

Commonly discussed symptoms

  • Persistent pain or discomfort in the upper abdomen.
  • Quickly feel full and lose weight.
  • Nausea or vomiting, sometimes bloody.
  • Black stools.
  • Fatigue due to anemia.

These symptoms are not specific. A doctor still needs to assess the cause.

Risk factors

  • Untreated Helicobacter pylori infection.
  • History of atrophic gastritis or precancerous conditions of the stomach.
  • History of smoking and consumption of certain foods.
  • Family history of gastric cancer in some cases.

What shapes the options?

Treatment discussions usually follow this path. The more complete each step is, the more focused the discussion with your doctor becomes.

  1. Diagnosis

    Confirmed through pathology review.

  2. Subtype

    3 subtypes discussed on this page.

  3. Stage

    Staging uses the TNM system by assessing the depth of invasion of the stomach wall and lymph node involvement.

  4. Biomarkers

    Relevant markers: HER2, PD-L1, MSI / MMR, CLDN18.2.

  5. Treatment history

    Each previous line affects the next option.

  6. Progression?

    If the disease progresses, reassessment and molecular testing are usually discussed.

  7. Next step

    Further evaluation, clinical trials, or a second opinion.

Stage I

Tumour limited to the stomach lining without spread to distant nodes.

Stage II

A deeper tumour or involvement of several nearby lymph nodes.

Stage III

Tumour involving more lymph nodes or nearby structures.

Stage IV

Cancer has spread to distant organs, including possible abdominal lining spread.

Relevant biomarkers

Molecular testing shapes categories, not decisions

Biomarker results open categories worth discussing. The final choice still considers stage, general condition, treatment history and the doctor's assessment.
Diagram CLDN18.2: ekspresi pada sel lambung, pemeriksaan, jalur disetujui vs investigasional, uji klinis

Visual explainer

CLDN18.2 in stomach cancer

What a positive CLDN18.2 result means and which questions are worth asking next.

Read the CLDN18.2 explainer
Ilustrasi reseptor di permukaan sel dengan molekul ligan yang mendekat

  • HER2

    HER2 is a protein on the surface of cells that can promote growth.

    Immunohistochemistry (IHC) · FISH (fluorescence in situ hybridisation)

    View biomarker →

  • PD-L1

    PD-L1 is a protein that can help cancer cells evade the immune system.

    PD-L1 immunohistochemistry · Tumour tissue biopsy

    View biomarker →

  • MSI / MMR

    Cells have a DNA repair system.

    MMR immunohistochemistry · MSI PCR

    View biomarker →

  • CLDN18.2

    CLDN18.2 is a protein that is usually found in gastric cells and can also be found in gastric cancer cells.

    CLDN18.2 immunohistochemistry · Tumour tissue biopsy

    View biomarker →

Progression and resistance concepts

  • Progression in gastric cancer can take the form of local tumor growth, the appearance of fluid in the stomach, or spread to other organs.
  • Marker examination after progression may change, so resampling is sometimes considered.
  • Differences in HER2 status between initial and post-therapy tumors are one of the reasons re-examination is discussed.
  • The next choice usually takes into account the therapy already undertaken, general condition, and the availability of clinical trials.

Treatment options commonly discussed

The actual order and combination are always determined by the team directly examining the patient.

When are clinical trials discussed?

Trial group and treatment history

The studies below are filtered from the public registry. International patient access and site readiness have not been verified.

Clinical trials are usually discussed after standard pathways are mapped, or when biomarker results point to a specifically studied group. There are currently 60 registry records related to Stomach cancer, and 13 mention a specific biomarker.

View all 60 studiesCheck my case match

What should be prepared for a second opinion?

Records usually requested

  • Endoscopy and pathology reports.
  • HER2, PD-L1, MSI/MMR, and CLDN18.2 examination results if available.
  • Recent CT scan or PET-CT.
  • Records of previous operations if they have been performed.
  • Notes on therapy and response.

Questions for the oncologist

  • What is the histological type of my gastric cancer, and is there CLDN18.2 information?
  • Was my HER2 checked, what was the score, and was the assessment done on a recent sample?
  • What is my MSI/MMR status and do the results affect treatment discussions?
  • Is surgery possible, and if not, why?
  • Are there any clinical trials relevant to my marker?

Have CLDN18.2 and HER2 been tested on the tumour tissue?

Not sure about the next step for Stomach cancer?

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Deeper references

A reference section for readers who want details on subtypes, drugs, or every study record.

Intestinal-type stomach adenocarcinoma

Draft, not yet medically reviewed

A stomach adenocarcinoma subtype resembling glands and often linked to H. pylori infection and precancerous conditions.

Intestinal type is often discussed through the markers HER2, MSI/MMR, and PD-L1. The growth pattern influences how the tumor spreads and how surgery is planned.

Relevant markers

HER2PD-L1MSI / MMR

Stage note

Assessment of the depth of invasion and lymph nodes is an important part of staging.

Diffuse-type stomach adenocarcinoma

Draft, not yet medically reviewed

A stomach adenocarcinoma subtype that spreads within the stomach wall without forming a clear mass, making early detection harder.

The diffuse type is less likely to show HER2 expression and may be associated with changes in the CDH1 gene. Peritoneal involvement is more frequently discussed, so imaging studies and peritoneal markers become relevant.

Relevant markers

CLDN18.2MSI / MMRPD-L1

Stage note

Because of submucosal spread, the stage is often more advanced when diagnosis and peritoneal evaluation becomes important.

Gastro-oesophageal junction adenocarcinoma

Draft, not yet medically reviewed

A tumour at the junction of the oesophagus and stomach, discussed with marker considerations similar to stomach cancer.

This group is often assessed with HER2, PD-L1, and MSI/MMR, and in some cases also CLDN18.2. The surgical plan depends on the location of the tumor relative to the diaphragm.

Stage note

Measurement of tumor location and gland involvement determines the surgical approach and sequence of therapy.

Frequently asked questions

Short answers to the most common questions; full explanations are in the sections above.

How is gastric cancer usually diagnosed?

Endoscopy with biopsy is the diagnostic basis, followed by imaging to define stage. Most gastric cancers are adenocarcinomas, with intestinal and diffuse types behaving differently.

Which markers affect gastric cancer treatment discussion?

The page discusses HER2, PD-L1, MSI/MMR, and CLDN18.2. A useful pathology report states histology, HER2 score, MSI/MMR status, and when available CLDN18.2 percentage and intensity.

What should I ask if the pathology marker report is incomplete?

Ask whether HER2 has been tested, what the score is, and whether the sample is recent; whether CLDN18.2 is reported; and what the MSI/MMR status is. These questions are included in the page's second-opinion section.

What does stage IV mean in gastric cancer?

Stage IV means cancer has spread to distant organs, including possible spread to the abdominal lining. Staging uses TNM, including depth of stomach-wall invasion and lymph-node involvement.

Why is marker retesting sometimes discussed after progression?

Marker findings can change after progression, so repeat sampling may be considered. A change in HER2 status between the original tumor and later disease is one reason retesting is discussed; later choices also consider prior therapy, condition, and trial availability.

Related explainers

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