Gastric cancer immunotherapy: how PD-L1 and MSI affect the choice

Start with the treatment setting

A patient with a removable tumor preparing for surgery and a patient with metastatic gastric cancer are asking different questions. In the first situation, treatment may be intended to lower recurrence risk around an operation. In the second, systemic disease control and symptoms are central.

Ask whether the proposed immune drug is being used before surgery, after surgery or for disease that cannot be removed. The supporting trial and local indication should match that setting. A familiar drug name can appear in several plans with different eligibility and companion medicines.

Sources and references: [1] [2]

What PD-L1 CPS adds

The combined positive score incorporates PD-L1 staining in tumor cells and certain immune cells. It is not the same measure as a tumor proportion score used in some other cancers. Ask for the numerical result and the testing method.

The score can influence whether a particular immune combination is appropriate and how its likely benefit is discussed. Thresholds differ between regimens and jurisdictions. A result described simply as positive may leave too much ambiguity for choosing treatment.

Sources and references: [1] [3]

Why MSI/MMR deserves a separate look

MSI-H and dMMR identify a DNA repair-related tumor characteristic that can support checkpoint-inhibitor treatment in defined circumstances. They are different from PD-L1 expression and should not be inferred from a CPS result.

If the MSI and protein-staining results are inconsistent, ask for pathology review. A limited biopsy may also need additional testing. The useful question is whether the final interpretation changes the recommended plan now, including how it affects a surgery-based strategy when the cancer remains removable.

Sources and references: [4] [1]

HER2 helps determine the combination

For HER2-positive advanced gastric or gastroesophageal junction adenocarcinoma, the US FDA approved pembrolizumab with trastuzumab and fluoropyrimidine-platinum chemotherapy for first-line treatment when PD-L1 CPS is at least 1. The HER2 and CPS requirements are both part of that decision.

HER2-negative disease has other immune-plus-chemotherapy pathways, with eligibility depending on the selected regimen. CLDN18.2 positivity may introduce a separate targeted option. Ask the oncologist how the results are being weighed together and why one combination is preferred.

Sources and references: [3] [1] [5]

Immunotherapy around surgery has its own evidence

Durvalumab with FLOT chemotherapy before and after surgery, followed by durvalumab, received US approval in November 2025 for resectable gastric or gastroesophageal junction adenocarcinoma. If you are considering this option, ask the team to map the preoperative and postoperative phases onto your surgery plan.

Discuss surgical timing, recovery and the expected postoperative treatment. If you have already had surgery or cannot tolerate FLOT, ask whether the evidence for the proposed alternative still fits. A team in China should confirm the locally applicable indication and access arrangements.

Sources and references: [2]

Who needs extra safety discussion?

Autoimmune disease, organ transplantation and immune-suppressing medicines can alter the risk of checkpoint inhibitors. Tell the oncologist about these before the plan is finalized. Baseline bowel, breathing and endocrine symptoms are also worth recording.

Immune reactions may affect the bowel, lungs, liver or hormone-producing glands. Persistent diarrhea, a new cough, shortness of breath, jaundice or an unusual change in energy needs prompt contact with the treating team. Severe or rapidly worsening symptoms require urgent medical assessment.

Sources and references: [6]

Agree on response checks and treatment changes

The team follows symptoms, scans and blood tests to judge whether the combination is useful and tolerable. Ask when response will be assessed and which drug would be paused or adjusted if a side effect develops. Combination treatment can make the cause of a symptom less obvious.

If you return home between visits, arrange a clinician who can assess new symptoms and communicate with the treating center. Carry the immune drug name and infusion dates. Some immune effects can appear after treatment has stopped, so the history remains relevant to later medical visits.

Sources and references: [6] [1]

Turn the test reports into a focused consultation

A gastric oncology inquiry in Shanghai can be directed through a resource such as Fudan University Shanghai Cancer Center. Prepare the complete HER2, PD-L1 and MSI/MMR reports rather than only the result summaries.

EastMedGo can help coordinate the records and practical questions for a specialist review. Through contact, share whether surgery is planned, the proposed regimen and any autoimmune condition. We can help clarify consultation arrangements and the information the receiving team needs to compare your options.

Sources and references: [7]

Common questions