TRASTUZUMAB DERUXTECAN (T-DXd)
FOR HER2-POSITIVE GASTRIC CANCER
A complete guide to T-DXd (Enhertu) in HER2-positive gastric cancer โ the DESTINY-Gastric01 trial that changed second-line treatment, who qualifies, what to expect, and how to access T-DXd at specialist centres in China.
analyticsAt a Glance
- check_circleT-DXd (Enhertu) achieved 51% ORR at second line vs 14% with chemotherapy in DESTINY-Gastric01
- check_circleNow standard second-line therapy for HER2+ gastric cancer after trastuzumab-containing first-line treatment
- check_circleT-DXd has received NMPA approval in China โ available at major gastric cancer centres
- check_circleInterstitial lung disease (ILD) is the key safety signal requiring monitoring throughout treatment
What Is Trastuzumab Deruxtecan (T-DXd)?
Trastuzumab deruxtecan (T-DXd, brand name Enhertu, also known as DS-8201a) is an antibody-drug conjugate (ADC) โ a new class of oncology agent that combines the targeting precision of a monoclonal antibody with the cytotoxic potency of a chemotherapy payload, delivered selectively to HER2-expressing tumour cells.
โT-DXd is not simply a more potent version of trastuzumab โ it is a fundamentally different type of drug that delivers chemotherapy directly inside HER2-expressing cancer cells.โ
The Antibody Component โ Trastuzumab
T-DXd uses the same trastuzumab antibody that has been in clinical use since the ToGA trial โ binding with high affinity and specificity to the HER2 extracellular domain on tumour cell surfaces. This targeting component directs the entire ADC molecule to HER2-expressing cancer cells.
The Payload โ DXd (Deruxtecan)
Attached to the trastuzumab is a topoisomerase I inhibitor payload (deruxtecan, DXd) โ a potent chemotherapy agent that, once internalised into the cancer cell, causes fatal DNA damage. Critically, DXd also kills neighbouring HER2-negative cells through a 'bystander effect' โ extending activity beyond strictly HER2-positive cells.
High Drug-to-Antibody Ratio (DAR 8)
T-DXd carries a drug-to-antibody ratio of 8 โ meaning eight DXd molecules are attached per trastuzumab antibody. This is substantially higher than older ADCs like T-DM1 (DAR ~3.5), producing a much higher intracellular cytotoxic concentration upon HER2 binding and internalisation.
Bystander Effect
The membrane-permeable DXd payload, once released inside a HER2+ cell, can diffuse into adjacent HER2-negative tumour cells โ killing them through the bystander effect. This explains T-DXd activity in HER2-low and even HER2-heterogeneous tumours.
DESTINY-Gastric01 and DESTINY-Gastric02 โ Key Results
The pivotal clinical trials that established T-DXd as the second-line standard for HER2-positive gastric cancer โ producing response rates and survival outcomes previously unseen at this line of therapy.
DESTINY-Gastric01: T-DXd vs Chemotherapy (2nd Line, HER2+, Asian Patients)
T-DXd vs irinotecan or paclitaxel in HER2+ advanced gastric/GEJ cancer after โฅ2 prior regimens. Source: Shitara et al., NEJM 2020.
- ORR: T-DXd51.3%
- ORR: chemotherapy14.3%
- Median OS: T-DXd12.5 months
- Median OS: chemo8.4 months
DESTINY-Gastric02: T-DXd in Western HER2+ Gastric Cancer Patients (2nd Line)
Single-arm study of T-DXd in Western patients with HER2+ gastric/GEJ cancer after trastuzumab-based first-line. Source: Van Cutsem et al., JCO 2023.
- Confirmed ORR: T-DXd (Western patients)41.8%
- Median OS: T-DXd12.1 months
T-DXd Eligibility โ What Is Required
A structured reference of the eligibility criteria for T-DXd in HER2-positive gastric cancer, based on the approved label and pivotal trial criteria.
| Criterion | Required Status | Notes |
|---|---|---|
| HER2 IHC status | IHC 3+ or IHC 2+ confirmed | T-DXd is approved for IHC 3+ or IHC 2+ (ISH not required for T-DXd in most approvals) |
| Prior HER2-directed therapy | Prior trastuzumab-containing regimen | T-DXd is 2nd-line after progression on trastuzumab + chemotherapy |
| ECOG PS | 0โ1 (DESTINY-Gastric01) | PS 2 patients assessed case-by-case; major trial enrolled PS 0โ1 |
| Lung function | No pre-existing ILD or pneumonitis | Active ILD is a contraindication due to T-DXd ILD risk |
| Organ function | Adequate hepatic and renal function | Standard ADC eligibility criteria โ bilirubin, creatinine, LFT thresholds apply |
| HER2-low | IHC 1+ or IHC 2+/ISH negative | Not approved for gastric cancer in HER2-low โ trials ongoing |
T-DXd Safety Profile โ What Patients Should Know
T-DXd has a distinct safety profile dominated by the risk of interstitial lung disease (ILD) โ a clinically serious adverse event requiring active monitoring and prompt management.
Common and Manageable Side Effects
- Nausea (most common)Reported in ~74% of patients โ predominantly grade 1โ2 and manageable with antiemetic prophylaxis. Significantly less frequent than with conventional chemotherapy in many patients.
- FatigueFatigue was reported in ~59% โ largely grade 1โ2, manageable with rest and supportive care, and not typically dose-limiting.
- AlopeciaHair loss occurs in approximately 30% of patients โ expected with the DXd topoisomerase I inhibitor payload component.
- MyelosuppressionNeutropenia, anaemia, and thrombocytopenia occur at rates comparable to standard chemotherapy โ managed with standard haematological monitoring and support.
Serious Side Effects Requiring Monitoring
- Interstitial Lung Disease (ILD) โ Key Safety SignalILD occurred in ~10โ15% of patients in DESTINY trials (any grade); grade 3โ4 in ~1โ3%. Requires mandatory monitoring with regular chest CT โ promptly discontinue T-DXd and initiate corticosteroids if ILD is diagnosed.
- Embryo-Fetal ToxicityT-DXd is contraindicated in pregnancy. Women of childbearing potential must use contraception during and for 7 months after treatment.
- Cardiotoxicity (less common than trastuzumab)Cardiac function (LVEF) should be assessed before treatment and periodically during T-DXd โ though cardiac toxicity appears less frequent than with standard trastuzumab.
ILD Monitoring During T-DXd Treatment
Interstitial lung disease (ILD) is the most important safety consideration with T-DXd. Active monitoring at every treatment visit is mandatory.
- 1
Baseline Chest CT Before Starting T-DXd
A CT chest (high-resolution where possible) should be performed before the first T-DXd dose โ providing a baseline to compare against if respiratory symptoms develop during treatment.
- 2
Respiratory Symptom Inquiry at Every Visit
At each clinic visit and before each infusion, patients are asked about new or worsening cough, shortness of breath, fever, or decreased exercise tolerance โ the early symptoms of T-DXd ILD.
- 3
CT Chest at First Sign of Symptoms
Any new respiratory symptoms should trigger immediate CT chest. Radiological findings of ILD range from ground-glass opacification to consolidation and interstitial infiltrates.
- 4
Dose Hold or Discontinuation Based on ILD Grade
Grade 1 ILD: dose hold and monitoring. Grade 2: dose hold + corticosteroids; may resume if resolved. Grade 3โ4 or recurrent Grade 2: permanent discontinuation of T-DXd.
T-DXd in Gastric Cancer โ Key Numbers
The most important quantitative benchmarks from the pivotal T-DXd gastric cancer trials.
- 51.3%ORR with T-DXd at second-line (DESTINY-Gastric01)More than 3.5 times the response rate of chemotherapy at the same line โ the most impactful second-line result in HER2+ gastric cancer history.
- HR 0.59OS hazard ratio: T-DXd vs chemotherapy (DESTINY-Gastric01)A ~41% reduction in mortality risk vs standard second-line chemotherapy โ a statistically and clinically significant survival benefit.
- ~10โ15%ILD incidence (any grade) in DESTINY gastric trialsThe key safety signal requiring mandatory monitoring โ early detection and prompt steroid treatment are essential to prevent severe ILD.
More from the Gastric Cancer Resource Library
Continue exploring gastric cancer treatment โ from HER2 testing and CLDN18.2 therapy to immunotherapy and treatment access in China.
Frequently Asked Questions About T-DXd in Gastric Cancer
My gastric cancer is HER2 IHC 2+ but ISH was not done. Can I receive T-DXd?
T-DXd approval criteria in many markets โ including China's NMPA approval โ cover HER2 IHC 3+ and IHC 2+ patients without necessarily requiring ISH confirmation for T-DXd eligibility (unlike trastuzumab, which requires ISH confirmation of IHC 2+ cases). This is because T-DXd's bystander effect means it maintains activity across a broader HER2 expression spectrum. However, specific eligibility criteria vary by country and prescribing institution. CancerFax confirms the applicable eligibility criteria at the treating centre for your specific IHC result.
Can T-DXd be used in the first-line setting before trastuzumab?
T-DXd is currently approved at second-line for HER2+ gastric cancer โ after prior trastuzumab-containing therapy. First-line T-DXd trials (DESTINY-Gastric05 and others) are ongoing. Until first-line trial data matures, trastuzumab + chemotherapy (ยฑ nivolumab) remains the standard first-line approach, with T-DXd reserved for the second-line setting. CancerFax can identify patients eligible for first-line T-DXd trials at Chinese centres.
Is T-DXd (Enhertu) available in China and how does CancerFax help access it?
Yes โ T-DXd received NMPA approval in China for HER2-positive gastric cancer and is available at major academic cancer centres. RC48 (disitamab vedotin), a Chinese-developed HER2 ADC with NMPA approval, is an additional option. CancerFax reviews your HER2 status and prior treatment history, identifies centres with confirmed T-DXd or RC48 availability, obtains treatment cost estimates, and coordinates the full logistics of your visit including consultation, infusion scheduling, and ILD monitoring planning.
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 HER2-Positive Gastric Cancer Progressed on Trastuzumab?
CancerFax reviews your HER2 status, prior treatment history, and current disease extent to confirm T-DXd eligibility and coordinates access at specialist Chinese gastric cancer centres where it is clinically available.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified oncologist before making treatment decisions.