Medical Oncologist
Stomach & gastroesophageal cancer
Targeted Therapy for — Stomach and Gastroesophageal Cancer
Whether targeted therapy is right for your stomach or gastroesophageal junction cancer depends entirely on biomarker tests done on your tumour tissue. The results directly change which treatment is recommended — which is why testing happens before any decision is made.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed August 2026
- HER2 is tested first — HER2 is the most common actionable marker in stomach and GEJ cancer and the one that most directly affects first-line treatment.
- Testing uses your existing biopsy — In most cases the tissue sample from your diagnostic biopsy is enough — you do not need a separate procedure.
- Multiple markers matter — HER2, PD-L1, MSI status and newer markers are tested together, because more than one result can influence your treatment plan.
- A negative result is still useful — Knowing which markers are absent narrows the options and avoids treatments unlikely to help you specifically.
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Targeted therapy for stomach and gastroesophageal cancer is decided by biomarker tests on your tumour tissue. HER2 status is the most important marker to establish first. NCCN and ESMO both recommend testing all patients at diagnosis, because the result directly changes which first-line treatment is recommended.
Which markers are tested in stomach and gastroesophageal cancer?
- HER2 (ERBB2)
- Protein overexpression or gene amplification on the tumour cell surface. Tested by IHC first, then FISH if the result is borderline. A positive result opens access to HER2-targeted treatment in combination with chemotherapy — recommended in first-line by NCCN, ESMO and ASCO.
- PD-L1 (CPS)
- The combined positive score measures how much of the tumour and surrounding tissue expresses the PD-L1 protein. A higher score predicts a greater likelihood of response to checkpoint immunotherapy. It is routinely tested alongside HER2.
- MSI and dMMR
- Microsatellite instability and deficient mismatch repair indicate that the tumour carries an unusually high number of mutations. Tumours with this profile tend to respond well to immunotherapy and may be eligible for treatment options not available to MSS tumours.
- CLDN18.2 (Claudin 18.2)
- A protein expressed on the surface of some stomach cancer cells. A CLDN18.2-targeted antibody has received regulatory approval for use in CLDN18.2-positive, HER2-negative tumours in combination with chemotherapy. Testing for this marker is increasingly recommended alongside standard panels.
- VEGFR2
- Vascular endothelial growth factor receptor 2. A VEGFR2-targeted antibody is used in approved later-line indications without requiring a specific biomarker score — unlike HER2 or CLDN18.2, where test positivity determines eligibility.
- FGFR2b
- Fibroblast growth factor receptor 2b. An emerging target under active clinical investigation. Testing may be offered as part of an extended panel at some centres, but it is not yet part of routine standard-of-care testing according to current NCCN or ESMO guidance.
What does a positive HER2 result actually mean for your treatment?
A HER2-positive result means your tumour overexpresses or amplifies the HER2 protein, and that protein is driving part of the cancer's growth. Targeted treatment aims to block that driver directly.
NCCN and ESMO guidance recommends combining HER2-targeted treatment with chemotherapy as the first-line approach for HER2-positive gastric and GEJ cancers. Adding checkpoint immunotherapy to that combination is also recommended for tumours where the PD-L1 score meets the threshold your oncologist will explain.
A negative HER2 result does not mean targeted therapy is off the table. It means your oncologist will look at the other marker results — PD-L1, MSI, CLDN18.2 — to see which options apply to you.
What should you ask before your treatment starts?
- Ask for the full biomarker panel results in writing — HER2, PD-L1 CPS, MSI status, and CLDN18.2 if tested.
- Ask which markers came back positive and which treatment options those results open up.
- Ask which markers were not tested and whether they are relevant to your cancer type and stage.
- Ask whether re-testing is recommended if your disease changes or progresses.
- Tell your team about any supplements, herbal preparations or traditional medicines you are taking, as some can interact with targeted therapies.
- Ask what to watch for in the first weeks of treatment and which symptoms need a same-day call.
Meet the Specialists
17+ senior cancer specialists. One panel for your case.
Trained at AIIMS, Tata Memorial, and leading international centres. Combined 150+ years of experience. Every complex case is reviewed by 3+ of them — together.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
Surgical Oncologist
Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
Radiation Oncologist
Radiation Oncologist
Radiation Oncologist
Hematologist
Interventional Radiologist
Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
Surgical Oncologist
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How is targeted therapy given for stomach cancer?
Most targeted therapies and immunotherapy combinations for stomach and GEJ cancer are given by intravenous infusion. At CION centres, these are administered as day-care infusions — you come in, receive the treatment, and go home the same day.
The schedule depends on which agents your oncologist recommends. Chemotherapy cycles typically continue for a defined number of rounds; targeted therapies may continue beyond that depending on response and tolerability.
PET-CT scans and other response-assessment imaging are coordinated with partner imaging centres. Your oncologist will explain when scans are scheduled and what the results mean for continuing treatment.
How does the path from testing to treatment work?
Biopsy tissue is sent for biomarker testing
Your oncologist sends the tumour tissue from your diagnostic biopsy to the pathology laboratory. In most cases no new procedure is needed. If the original sample was too small, a repeat biopsy may be required.
HER2 is tested by IHC, then FISH if the result is borderline
IHC measures the amount of HER2 protein on the tumour surface. A borderline IHC result is confirmed by FISH, which looks directly at the gene copy number. Results typically take one to two weeks from when the sample arrives at the laboratory.
PD-L1, MSI and CLDN18.2 are tested in parallel
These tests are usually run on the same tissue block at the same time, so you receive the full panel together rather than waiting for each result separately.
Your oncologist reviews all results together
Results are reviewed in the context of your stage, overall health and treatment history. The recommendation reflects all the results together — not any single marker in isolation.
Treatment plan is discussed and agreed with you
Your oncologist explains which treatment is recommended, what it is intended to achieve, and what to watch for. You have the opportunity to ask questions and, if you choose, to seek a second opinion before starting.
Treatment starts as a day-care infusion at CION
Once the plan is agreed, infusions are scheduled at your nearest CION centre. Standard targeted therapy and immunotherapy combinations do not require an overnight stay.
What happens if none of the markers come back positive?
A panel where HER2 is negative, PD-L1 is low and MSI is stable does not leave you without options. Chemotherapy remains effective for stomach and GEJ cancer and is the backbone of treatment for most patients.
Your oncologist will explain which regimen is most appropriate for your stage and situation, what it is expected to achieve, and what comes next depending on how the disease responds.
Eligibility can change over time. If your cancer progresses or new evidence becomes available for your tumour profile, it is reasonable to ask whether the biomarker question should be revisited.
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Common questions
Frequently asked questions
Is HER2 testing done automatically for all stomach cancer patients in India?
NCCN and ESMO guidance recommends HER2 testing for all patients with gastric or gastroesophageal junction adenocarcinoma at the time of diagnosis. In practice, whether it happens automatically depends on the centre. If you have not been told your HER2 status and your oncologist has not raised it, ask directly — it is a reasonable question and one your team should be able to answer from your existing biopsy.
Can I be HER2-positive in stomach cancer like in breast cancer?
Yes, HER2 overexpression or amplification occurs in both breast and stomach cancers, but the way it is scored and the treatments recommended differ. The IHC scoring system used for stomach cancer has different thresholds than the one used for breast cancer, and the HER2-targeted treatments in stomach cancer are not always the same agents used in breast cancer. A HER2 result from a previous breast cancer diagnosis does not apply to your stomach cancer.
How long does it take to get biomarker results back?
Standard HER2 testing by IHC typically takes a few days to one week once the laboratory receives the sample. FISH confirmation, if needed, adds more time. When PD-L1, MSI and CLDN18.2 are run in parallel on the same block, the full panel result is usually available within one to two weeks. Testing that needs to go to a specialist laboratory can take longer. Ask your team when the sample was sent and when you can expect results.
What is CLDN18.2 and should I ask to be tested for it?
Claudin 18.2 is a protein found on the surface of some stomach cancer cells. A CLDN18.2-targeted antibody has received regulatory approval for CLDN18.2-positive, HER2-negative stomach and GEJ cancers in combination with chemotherapy. Whether CLDN18.2 testing is part of your panel depends on your centre and the treatments available to you. It is a reasonable marker to ask your oncologist about, particularly if your HER2 result is negative.
My cancer has spread to other organs — can I still have targeted therapy?
Yes. Most targeted therapy options for stomach and GEJ cancer have been studied and approved specifically in the advanced or metastatic setting. Biomarker results, not the extent of spread alone, determine eligibility. Your oncologist will also assess your overall health and organ function alongside the marker results, as both affect which treatments are appropriate.
Can targeted therapy be combined with surgery?
For most patients with gastric or GEJ cancer, targeted therapy has been studied primarily in the advanced or metastatic setting. Whether any component of your treatment plan is used before or after surgery — and whether surgery is part of your plan — depends on your stage and how your tumour responds. This is a decision your oncologist will make based on your individual situation, and it is worth asking about explicitly if surgery has been discussed.