HER2-POSITIVE GASTRIC CANCER:
FROM TRASTUZUMAB TO T-DXd
A complete guide to HER2-positive gastric cancer โ how HER2 is tested, what treatments are available at each line of therapy, and how to access the most advanced HER2-directed options including T-DXd and investigational cellular therapies in China.
analyticsAt a Glance
- check_circleHER2 positivity occurs in ~15โ20% of gastric cancers โ the most important actionable biomarker in this disease
- check_circleTrastuzumab + chemotherapy remains first-line standard; T-DXd is now standard at second-line
- check_circleHER2-directed CAR-T cell therapy trials are actively recruiting at Chinese academic centres
- check_circleCancerFax coordinates access to HER2+ gastric cancer specialists and T-DXd at Chinese centres
What Is HER2-Positive Gastric Cancer?
HER2 (Human Epidermal Growth Factor Receptor 2) is a transmembrane tyrosine kinase receptor that drives cell proliferation when overexpressed or amplified. In gastric cancer, HER2 positivity โ defined as IHC 3+ or IHC 2+/ISH amplified โ occurs in approximately 15โ20% of tumours and is associated with more aggressive disease biology and, critically, with eligibility for highly effective targeted therapies.
โHER2 positivity in gastric cancer is not bad news โ it is actionable news. A defined molecular target means a defined therapeutic opportunity.โ
How HER2 Is Tested
HER2 status is determined by IHC (immunohistochemistry) followed by ISH (in situ hybridisation) for IHC 2+ equivocal cases. A score of IHC 3+ (strong complete membranous staining in >10% of tumour cells) is positive. IHC 2+ with ISH amplification is also positive. IHC 0, 1+, or 2+/ISH non-amplified is HER2-negative.
HER2 IHC Scoring in Gastric Cancer โ Different From Breast Cancer
HER2 IHC scoring criteria in gastric cancer differ from breast cancer โ basolateral or lateral membrane staining (rather than full circumferential) is accepted as positive in gastric cancer. This distinction matters: applying breast cancer scoring criteria to gastric biopsies can lead to false-negative HER2 results.
Re-testing at Progression
HER2 status can change between primary diagnosis and metastatic recurrence โ and between first-line and subsequent lines of therapy. Re-biopsy and HER2 re-testing at progression is recommended, particularly before initiating T-DXd, to confirm continued HER2 positivity.
HER2-Low Gastric Cancer
HER2-low (IHC 1+ or IHC 2+/ISH non-amplified) gastric cancer is an emerging category of interest โ T-DXd has demonstrated activity in HER2-low breast cancer, and trials are exploring this in gastric cancer. HER2-low patients do not qualify for standard trastuzumab but may access T-DXd through clinical trials.
HER2-Positive Gastric Cancer: Treatment by Line
The treatment landscape for HER2-positive gastric cancer has expanded dramatically since the ToGA trial in 2010. Each line of therapy now has a distinct evidence base and set of options.
| Treatment Line | Preferred Regimen | Key Trial | Notes |
|---|---|---|---|
| First line | Trastuzumab + FOLFOX/CAPOX ยฑ nivolumab (if CPS โฅ5) | ToGA (2010) + CheckMate-811 | Adding nivolumab to trastuzumab + chemo: ongoing evaluation |
| Second line | Trastuzumab deruxtecan (T-DXd, DS-8201) | DESTINY-Gastric01/02 (2021โ2023) | ORR ~40โ51% vs ~14% with chemotherapy; standard of care |
| Second line (if T-DXd unavailable) | Ramucirumab + paclitaxel ยฑ anti-HER2 | REGARD, RAINBOW | T-DXd is preferred when accessible |
| Third line+ | Clinical trial (CAR-T, bispecific antibody, ADC) | Phase I/II at Chinese centres | HER2-directed CAR-T and bispecific Ab trials actively recruiting |
| HER2+ + CLDN18.2+ co-positive | Trastuzumab + FOLFOX ยฑ zolbetuximab | Exploratory; under investigation | Co-positivity (~8โ10% of cases) โ combination being studied |
Key Trial Data: HER2-Positive Gastric Cancer
Landmark trial results that established and advanced HER2-directed therapy in gastric cancer โ from ToGA through to the T-DXd revolution.
ToGA Trial: Trastuzumab + Chemo vs Chemo Alone (1st Line, HER2+)
N=594. Trastuzumab + cisplatin/capecitabine vs chemotherapy alone in HER2+ advanced gastric/GEJ cancer. Source: Bang et al., Lancet 2010.
- Median OS: trastuzumab + chemo13.8 months
- Median OS: chemo alone11.1 months
DESTINY-Gastric01: T-DXd vs Chemotherapy (2nd Line, HER2+)
N=187. Trastuzumab deruxtecan vs irinotecan or paclitaxel in HER2+ advanced gastric cancer after โฅ2 prior lines. Source: Shitara et al., NEJM 2020.
- ORR: T-DXd (2nd line HER2+)51.3%
- ORR: chemotherapy (2nd line)14.3%
- Median OS: T-DXd12.5 months
- Median OS: chemotherapy8.4 months
Emerging HER2-Directed Approaches in China
Beyond trastuzumab and T-DXd, a new generation of HER2-directed therapies is being developed and trialled primarily at Chinese academic centres.
HER2-Directed CAR-T Cell Therapy
Phase I/II trials at Chinese centres are evaluating CAR-T cells engineered with HER2-targeting chimeric antigen receptors in HER2+ gastric cancer โ offering a cellular immunotherapy option for patients progressing after T-DXd. Early data shows CAR-T activity in HER2 IHC 2+/3+ gastric tumours.
HER2 ร PD-1 Bispecific Antibodies
Novel bispecific antibodies (e.g. ZW25, KN026 + KN046) simultaneously targeting HER2 and PD-1/PD-L1 are in active Phase I/II development โ combining HER2-directed tumour killing with checkpoint disinhibition in a single molecule.
Zanidatamab (HER2 Bispecific ADC-Linked)
Zanidatamab simultaneously binds two distinct HER2 epitopes, producing anti-tumour activity through multiple mechanisms including receptor downregulation and ADCC. Active trials in HER2+ gastric cancer in China.
RC48 (Disitamab Vedotin โ Chinese HER2 ADC)
RC48 is a China-developed HER2-directed antibody-drug conjugate that has demonstrated activity in HER2-overexpressing gastric cancer โ including in patients with HER2 IHC 2+, offering potential benefit to a HER2-low population. NMPA approved in China.
HER2-Positive Gastric Cancer โ Key Numbers
The most clinically important figures for patients and families navigating HER2+ gastric cancer treatment decisions.
- 51.3%ORR with T-DXd at second-line (DESTINY-Gastric01)The T-DXd response rate at second line is more than triple that of standard chemotherapy โ transforming second-line HER2+ gastric cancer management.
- ~15โ20%Proportion of gastric cancers that are HER2-positiveA substantial minority โ but one with multiple treatment options unavailable to HER2-negative patients.
- RC48China-developed HER2 ADC with NMPA approvalDisitamab vedotin (RC48) is a Chinese domestic HER2 ADC available in China โ offering an additional option for HER2-overexpressing gastric cancer patients.
More from the Gastric Cancer Resource Library
Continue exploring โ from CLDN18.2-targeted therapy and immunotherapy to advanced treatment access in China.
Frequently Asked Questions About HER2-Positive Gastric Cancer
My HER2 IHC was 2+ but the ISH result is negative. Am I HER2-positive?
No. HER2 IHC 2+ alone is equivocal โ ISH (in situ hybridisation) or FISH testing is performed to determine whether HER2 gene amplification is present. IHC 2+ with ISH amplified = HER2-positive; IHC 2+ with ISH non-amplified = HER2-negative. If your ISH result is negative, standard trastuzumab is not indicated, but you may still be assessed for clinical trial eligibility (e.g. HER2-low T-DXd trials) depending on your IHC score.
Can I get trastuzumab deruxtecan (T-DXd) in China?
Yes. T-DXd (Enhertu, DS-8201a) has received NMPA approval in China for HER2-positive gastric/GEJ cancer at second-line. It is available at major academic cancer centres in Beijing, Shanghai, and Guangzhou. CancerFax confirms T-DXd availability and current pricing at the recommended centre as part of treatment coordination. Additionally, RC48 (disitamab vedotin) โ a China-developed HER2 ADC with NMPA approval โ is available as an alternative HER2-directed ADC option.
My gastric cancer progressed after trastuzumab. What are my options?
Progression after first-line trastuzumab is the primary indication for T-DXd at second-line โ the DESTINY-Gastric01 trial established T-DXd as standard with an ORR of 51% vs 14% for chemotherapy. Beyond T-DXd, options include ramucirumab + paclitaxel, clinical trials of HER2 ร PD-1 bispecific antibodies, HER2-directed CAR-T therapy (investigational), and zanidatamab. CancerFax identifies current open trials at Chinese centres specifically for HER2+ gastric cancer patients post-trastuzumab progression.
How CancerFax Helps
CancerFax is a specialist cancer access and patient-navigation platform. We help patients and families understand their options, organise medical records, coordinate hospital communication, and support cross-border treatment planning where appropriate.
We help collect and organise reports, scans, pathology, biomarker results, and treatment history for structured case review.
We communicate with hospitals or trial teams to assess whether a case may be suitable for further screening.
We support appointment coordination, document submission, translation, and direct communication with international departments.
For international patients, we help with practical coordination โ travel planning, hospital admission guidance, and local support.
If this option is not suitable, we help explore other relevant treatments, clinical trials, or advanced care pathways.
From inquiry through to follow-up, our coordinators provide a single point of contact for the family.
CancerFax does not guarantee treatment access, eligibility, or clinical outcome. Our role is to help patients access accurate information, structured review, and appropriate specialist pathways.
Has Your Gastric Cancer Tested HER2-Positive? Advanced Options Are Available.
CancerFax reviews your HER2 testing results and prior treatment history to identify whether trastuzumab, T-DXd, bispecific antibody therapy, or HER2-directed CAR-T clinical trial access is appropriate for your case at specialist centres in China.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified oncologist before making treatment decisions.