Trastuzumab Deruxtecan (Enhertu / T-DXd)
A HER2-directed antibody-drug conjugate for HER2-positive, HER2-low, and HER2-mutant cancers — including breast, gastric, lung, and selected solid tumors.
What is Trastuzumab Deruxtecan?
What it targets
HER2 protein overexpression on cancer cells, or activating HER2/ERBB2 mutation in lung cancer — the antibody guides the DXd payload selectively to HER2-expressing tumor cells.
Who it may help
Patients with HER2-positive, HER2-low, HER2-ultralow breast cancer; HER2-positive gastric/GEJ cancer; HER2-mutant NSCLC; or HER2 IHC 3+ solid tumors after prior treatment.
Why testing matters
HER2 IHC, ISH/FISH, or NGS testing is mandatory before Enhertu — the specific test required depends on cancer type, and accurate HER2 status determines eligibility.
Which cancers can Trastuzumab Deruxtecan treat?
Enhertu has FDA approval across several cancer types where HER2 expression or mutation plays a driving role.
| HER2-positive Metastatic Breast Cancer | FDA-approved as first-line therapy with pertuzumab in selected settings, and for patients who have received prior anti-HER2 therapy. DESTINY-Breast03 showed superior outcomes compared with T-DM1. |
| HER2-low Metastatic Breast Cancer | FDA-approved for unresectable or metastatic HER2-low breast cancer (IHC 1+ or IHC 2+/ISH-negative) after prior therapy. DESTINY-Breast04 established this as a landmark indication for a previously underserved population. |
| HER2-ultralow Metastatic Breast Cancer | FDA-approved for HR-positive HER2-low or HER2-ultralow metastatic breast cancer that has progressed after one or more endocrine therapies in the metastatic setting, based on DESTINY-Breast06 data. |
| HER2-positive Gastric / GEJ Cancer | FDA-approved for locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma after prior trastuzumab-based therapy. DESTINY-Gastric01 demonstrated improvement over standard chemotherapy. |
| HER2-mutant NSCLC | FDA-approved for unresectable or metastatic NSCLC with activating HER2/ERBB2 mutations after prior systemic therapy. Requires molecular testing (NGS). DESTINY-Lung02 showed durable responses in this molecularly defined population. |
| HER2-positive IHC 3+ Solid Tumors (Pan-Tumor) | FDA accelerated approval for unresectable or metastatic HER2-positive (IHC 3+) solid tumors after prior systemic therapy when no satisfactory alternatives exist. Covers biliary tract, colorectal, endometrial, ovarian, salivary gland, bladder cancer, and others. |
Are you eligible for Trastuzumab Deruxtecan?
Eligibility depends on confirmed HER2 status, cancer type, treatment history, and organ function. Your oncologist will assess all these factors together.
- HER2 status confirmed by validated testing: IHC, ISH/FISH for breast and gastric cancer; NGS or FDA-approved molecular test for NSCLC; IHC 3+ for pan-tumor solid tumor indication.
- Cancer type must match an approved indication: HER2-positive, HER2-low, or HER2-ultralow metastatic breast cancer; HER2-positive gastric or GEJ adenocarcinoma; HER2-mutant NSCLC; or HER2 IHC 3+ solid tumors.
- Prior treatment history as required by indication: previous anti-HER2 therapy for HER2-positive breast or gastric cancer; prior systemic therapy for NSCLC and pan-tumor solid tumor indications.
- Adequate lung function with no active or uncontrolled interstitial lung disease or pneumonitis — ILD history is a critical safety consideration before starting Enhertu.
- Adequate heart function: left ventricular ejection fraction should be within acceptable limits before starting HER2-directed therapy, assessed by echocardiogram or MUGA scan.
- Adequate liver function: liver enzyme elevations may require dose modification or treatment delay; significant hepatic impairment affects dosing decisions.
- Adequate blood counts: haemoglobin, neutrophil count, and platelet levels must be sufficient to safely start treatment.
- Women of childbearing potential must use effective contraception during treatment and for the required period after the last dose; Enhertu carries a boxed warning for embryo-fetal toxicity.
- No active uncontrolled infection, and no severe allergy or prior serious hypersensitivity to trastuzumab-containing products without oncologist assessment.
How does Trastuzumab Deruxtecan work?
- Step 1 — The antibody finds and binds HER2
- Step 2 — The drug is internalized into the cancer cell
- Step 3 — The linker breaks down and releases the payload
- Step 4 — DXd damages cancer-cell DNA
- Step 5 — Bystander effect on nearby cancer cells
Enhertu carries approximately 8 payload molecules per antibody — one of the highest drug-to-antibody ratios among approved ADCs — enabling potent activity even in HER2-low tumors.
Tests required before starting Trastuzumab Deruxtecan
These tests confirm eligibility, guide dosing, and establish safety baselines before Enhertu infusions begin.
| HER2 IHC | Measures HER2 protein expression on cancer cells using immunohistochemistry; determines HER2-positive (3+), HER2-low (1+ or 2+/ISH-negative), or HER2-ultralow status for breast and gastric cancer. |
| ISH / FISH for HER2 | Confirms HER2 gene amplification when IHC is 2+; required for HER2-positive gastric cancer eligibility and HER2-positive breast cancer confirmation. |
| NGS (Next-Generation Sequencing) | Detects activating HER2/ERBB2 mutations — mandatory for NSCLC eligibility; also useful for solid tumor eligibility and resistance analysis. Must be done at a validated laboratory. |
| CT / PET-CT / MRI scan | Assesses disease extent and tumor burden before treatment; establishes the baseline against which treatment response will be measured on follow-up scans. |
| Echocardiogram or MUGA scan | Checks left ventricular ejection fraction (LVEF) before HER2-directed therapy; repeated during treatment. Important because HER2-directed agents can affect heart function in some patients. |
| Complete Blood Count (CBC) | Baseline haemoglobin, WBC, neutrophil count, and platelet levels; closely monitored during treatment as Enhertu can cause myelosuppression. |
| Liver Function Tests (LFT) | Baseline liver enzyme levels (ALT, AST, bilirubin, alkaline phosphatase) needed before and during treatment; dose modifications may apply for elevated liver enzymes. |
| Kidney Function Tests | Serum creatinine and eGFR to assess renal function; informs overall treatment safety and supports dosing decisions. |
| Lung symptom review | A careful assessment of any current cough, breathlessness, or lung symptoms must be done before starting Enhertu to exclude existing ILD or pneumonitis, which is a key risk factor. |
| Pregnancy test | Required before starting Enhertu in women of childbearing potential due to the boxed warning for embryo-fetal toxicity. |
How is Trastuzumab Deruxtecan given?
Enhertu is given as an intravenous (IV) infusion in a hospital or oncology daycare unit. It is not a tablet or oral medicine — it must be administered by trained healthcare staff.
| Dose — breast cancer, NSCLC, solid tumors | 5.4 mg per kilogram of body weight, given as an IV infusion once every 3 weeks (21-day cycle). |
| Dose — HER2-positive gastric / GEJ cancer | 6.4 mg per kilogram of body weight, given as an IV infusion once every 3 weeks (21-day cycle). |
| Infusion administration | Prepared by pharmacy staff and administered through a peripheral or central venous line. The first infusion typically takes approximately 90 minutes; subsequent infusions may be given over 30 minutes if prior infusions were well tolerated. |
| Pre-medications | Antiemetic pre-medications (drugs to prevent nausea and vomiting) are usually given before each infusion. Your oncologist or infusion team will advise on the pre-medication schedule. |
| Missed infusion or delay | If a cycle is delayed due to side effects (e.g. low blood counts, lung symptoms, or liver enzyme elevations), the next infusion is given as soon as recovery is confirmed. Never delay without telling your oncologist. |
| Dose reduction | The FDA label allows dose reductions for significant toxicities such as Grade 2 or higher ILD/pneumonitis (which requires permanent discontinuation), severe nausea/vomiting, or severe myelosuppression. Up to two dose reductions are allowed. |
| Duration of treatment | Enhertu is continued until disease progression, unacceptable toxicity, or a change in treatment plan. There is no pre-defined maximum number of cycles — the decision is made based on response and tolerance. |
| Monitoring during treatment | Blood counts, liver enzymes, and cardiac function are checked at regular intervals. Patients must report any new cough, breathlessness, or fever immediately between scheduled visits. |
Clinical evidence and benefits of Trastuzumab Deruxtecan
Trastuzumab deruxtecan has demonstrated meaningful clinical benefit across multiple cancer types in well-designed clinical trials, supporting its use as a new standard of care in several HER2-related settings.
| DESTINY-Breast03 — HER2-positive metastatic breast cancer | T-DXd showed substantially superior progression-free survival and overall survival compared with T-DM1 (ado-trastuzumab emtansine) in previously treated HER2-positive metastatic breast cancer — establishing it as the preferred second-line standard in this setting. |
| DESTINY-Breast04 — HER2-low metastatic breast cancer | In a landmark trial, T-DXd demonstrated significantly improved progression-free survival and overall survival versus physician's choice chemotherapy in HER2-low metastatic breast cancer — the first time an HER2-directed therapy showed benefit in this previously ineligible population. |
| DESTINY-Breast06 — HER2-ultralow metastatic breast cancer | Extended benefit to patients with HR-positive HER2-low and HER2-ultralow metastatic breast cancer who had progressed on endocrine therapy, supporting a further expansion of the HER2 targetable population in breast cancer. |
| DESTINY-Gastric01 — HER2-positive gastric cancer | T-DXd demonstrated improved overall survival and higher response rates compared with standard chemotherapy in previously treated HER2-positive gastric or GEJ adenocarcinoma, where treatment options after first-line trastuzumab-based therapy were previously limited. |
| DESTINY-Lung02 — HER2-mutant NSCLC | In HER2-mutant metastatic NSCLC, T-DXd produced durable objective responses in a population with limited targeted therapy options after prior systemic treatment, establishing it as an important molecularly matched treatment option. |
| DESTINY-PanTumor02 — HER2-positive solid tumors | Meaningful response rates were observed across multiple HER2 IHC 3+ solid tumor types including biliary tract, colorectal, endometrial, ovarian, bladder, and other cancers, supporting the accelerated approval for a tumor-agnostic pan-tumor indication. |
| Bystander effect in HER2-heterogeneous tumors | The membrane-permeable DXd payload can affect nearby cancer cells with lower HER2 expression — this bystander effect helps explain efficacy in HER2-low and heterogeneous tumors and differentiates Enhertu from older HER2-directed ADCs such as T-DM1. |
Individual responses vary. These results represent clinical trial data in selected patient populations — your oncologist will explain what the evidence means for your specific case.
Side effects of Trastuzumab Deruxtecan
Unlike traditional chemotherapy that broadly affects many cells throughout the body, Enhertu is more targeted — but it still carries significant side effects that require careful monitoring throughout treatment. Most common side effects are manageable with supportive care, but some serious reactions require prompt medical attention.
| Nausea | Very common; typically managed with antiemetic pre-medications and supportive medicines. May be significant in the first few days after infusion. |
| Vomiting | Common; often associated with nausea. Persistent vomiting affecting food and fluid intake requires early medical review. |
| Fatigue | Common; may be related to anaemia, the drug itself, or the disease. Patients should report significant fatigue — it may indicate a blood count issue needing attention. |
| Low white blood cells (leukopenia) | Common; increases infection risk. Blood counts are monitored regularly. Fever during low white cell periods requires urgent assessment. |
| Low neutrophils (neutropenia) | Common; the most significant infection risk. Fever with low neutrophils (febrile neutropenia) is a medical emergency requiring immediate care. |
| Anaemia (low haemoglobin) | Common; may cause breathlessness, dizziness, and fatigue. Severe anaemia may require blood transfusion or treatment delay. |
| Low platelets (thrombocytopenia) | Common; may cause bruising, bleeding, or small red spots (petechiae) on the skin. Report any unusual bleeding. |
| Hair thinning or hair loss (alopecia) | Common; hair thinning or loss typically occurs during treatment and is often reversible after treatment ends. |
| Constipation | Common; usually manageable with dietary changes, hydration, and laxatives as advised by the medical team. |
| Diarrhea | Common; risk of dehydration if severe. Report loose stools early — anti-diarrheal medicine and hydration adjustments may be needed. |
| Liver enzyme elevation | Common on blood tests; usually asymptomatic but monitored closely. Significant elevations may require dose delay or reduction. |
| Reduced appetite | Common; may contribute to weight loss. Nutritional support or dietitian input may be helpful. |
| Low potassium (hypokalaemia) | Detected on blood tests; may cause muscle cramps, weakness, or heart rhythm concerns if significant. Replaced with supplements as needed. |
| Musculoskeletal pain | Common; includes body pain, joint pain, and muscle aches. Usually manageable with standard pain relief. |
| Interstitial lung disease / pneumonitis | Serious and potentially fatal; requires immediate reporting of any new respiratory symptoms. See urgent warning section below. |
| Left ventricular dysfunction | HER2-directed therapy can affect heart function in some patients; LVEF monitoring by echocardiogram or MUGA is conducted during treatment. |
Contact your doctor immediately if you develop:
- New or worsening cough, breathlessness, chest tightness, fever, or any new lung symptom — these may signal interstitial lung disease or pneumonitis, which can be life-threatening.
- Fever of 38°C or higher, with or without chills or sore throat — fever during low blood count periods is a medical emergency; do not wait until your next scheduled appointment.
- Unusual or excessive bleeding, significant bruising, blood in urine or stool, or small red spots (petechiae) on the skin — these may signal dangerously low platelet counts.
- Chest pain, heart palpitations, or unusual shortness of breath unrelated to lung inflammation — these should be assessed urgently for possible cardiac causes.
- Severe nausea or vomiting that prevents you from keeping food, water, or oral medicines down for more than 24 hours — dehydration risk requires prompt assessment.
- Severe or worsening diarrhea with signs of dehydration such as dizziness, dry mouth, or dark urine — requires immediate rehydration support and oncology review.
Safety precautions and drug interactions
Tell your oncologist and pharmacist about all medicines, supplements, and herbal products before starting Enhertu. Some interactions can reduce efficacy or increase toxicity.
- Strong CYP3A4 inhibitors (such as certain antifungals like ketoconazole, some HIV medicines, and clarithromycin) may increase DXd exposure and toxicity risk — your oncologist should review all current medications before starting.
- Strong CYP3A4 inducers (such as rifampicin, carbamazepine, phenytoin, and St John's Wort) may reduce DXd levels and potentially reduce treatment effectiveness — avoid where possible and discuss with your oncologist.
- Prior or concurrent chest or lung radiation may increase the risk of pulmonary toxicity including ILD/pneumonitis — inform your oncologist of any history of chest radiotherapy.
- Embryo-fetal toxicity: Enhertu has a boxed FDA warning for harm to unborn babies. Women of childbearing potential must use highly effective contraception during treatment and for 7 months after the last dose.
- Male patients with female partners of childbearing potential should use contraception during treatment and for 4 months after the last dose.
- Breastfeeding is not recommended during treatment with Enhertu and for 7 months after the last dose due to potential harm to the infant.
- Patients with a history of clinically significant ILD or pneumonitis should be assessed very carefully before starting Enhertu — active or uncontrolled lung inflammation is a contraindication.
- Reduced left ventricular ejection fraction (LVEF): prior treatment with cardiotoxic agents (especially anthracyclines) may increase the risk of cardiac effects. LVEF must be adequate before starting and is monitored during treatment.
- Avoid live or attenuated vaccines during and for a period after treatment with Enhertu, as immunosuppression from low blood counts may reduce vaccine effectiveness or increase infection risk.
Trastuzumab Deruxtecan combination treatments
Enhertu can be used as monotherapy or, in selected settings, in combination with other agents. The right combination depends on cancer type, treatment line, approval status, and patient fitness.
| Enhertu + Pertuzumab (first-line HER2+ metastatic breast cancer) | FDA-approved combination for first-line treatment of unresectable or metastatic HER2-positive breast cancer. Adding pertuzumab (another HER2-targeting antibody) to Enhertu targets HER2 through a complementary mechanism. |
| Enhertu monotherapy (after prior anti-HER2 therapy) | Used alone in HER2-positive metastatic breast cancer after prior trastuzumab-based therapy, in HER2-positive gastric/GEJ cancer after prior trastuzumab, in HER2-mutant NSCLC, and in HER2 IHC 3+ solid tumors. |
| Enhertu after trastuzumab + pertuzumab + chemotherapy | Standard sequencing in HER2-positive metastatic breast cancer where Enhertu is commonly used after first-line trastuzumab, pertuzumab, and taxane-based therapy. |
| Enhertu after endocrine therapy (HR+ HER2-low / HER2-ultralow) | In HR-positive HER2-low or HER2-ultralow metastatic breast cancer, Enhertu is used after one or more prior endocrine therapies in the metastatic setting. |
| Clinical trial combinations | Enhertu is being studied in combination with checkpoint inhibitors (PD-1/PD-L1 antibodies), CDK4/6 inhibitors, and other targeted agents across multiple cancer types. Patients whose disease has progressed may be eligible for combination trial access. |
| Next-line options after Enhertu | If Enhertu is not tolerated or stops working, next-line options vary by cancer type and may include other HER2-directed ADCs (such as disitamab vedotin in gastric cancer), tucatinib-based regimens, chemotherapy, or clinical trials of novel bispecific antibodies or next-generation ADCs. |
If Trastuzumab Deruxtecan stops working
Like most cancer medicines, resistance to Enhertu can develop over time. Understanding how and why this happens helps guide the choice of next treatment.
| HER2 expression loss or downregulation | Some cancers may reduce HER2 expression under selection pressure from treatment, limiting the antibody's ability to find and bind to enough cancer cells. Repeat biopsy or liquid biopsy after progression can help assess whether HER2 status has changed. |
| Bypass signaling pathway activation | Cancer cells may develop or activate alternative growth pathways (such as PI3K/AKT/mTOR, KRAS, or FGFR signaling) that bypass HER2 dependence, allowing the tumor to continue growing even when the HER2 pathway is blocked. |
| Payload-related resistance mechanisms | Resistance to the DXd topoisomerase I inhibitor payload may develop through upregulation of drug efflux pumps or changes in topoisomerase I expression, reducing the effectiveness of the payload inside the cancer cell. |
| NGS at progression | Next-generation sequencing of new biopsy tissue or liquid biopsy at progression is strongly recommended. This may identify new actionable mutations in EGFR, ALK, ROS1, BRAF, KRAS, MET, NTRK, or other targets relevant to the cancer type. |
| Next-line options in breast cancer | After Enhertu, options may include tucatinib-based regimens, lapatinib combinations, margetuximab, other HER2-directed agents, chemotherapy, hormone therapy (if HR-positive), or clinical trials of next-generation ADCs or bispecific antibodies. |
| Next-line options in gastric cancer | After Enhertu in gastric/GEJ cancer, options may include chemotherapy, ramucirumab, checkpoint immunotherapy (particularly in MSI-high or high TMB tumors), or clinical trials. |
| Next-line options in NSCLC | After Enhertu in HER2-mutant NSCLC, further treatment may include chemotherapy, immunotherapy if PD-L1 expression supports it, or clinical trials studying next-generation ADCs and HER2-targeted agents. |
| Second opinion and advanced access | If Enhertu has failed and next steps are unclear, a specialist oncology second opinion with an expert in HER2-targeted therapy or advanced lung, breast, or gastric oncology is strongly recommended. CancerFax can facilitate this across India, China, Singapore, and other international centres. |
Cost of Trastuzumab Deruxtecan by country
Enhertu is a premium antibody-drug conjugate and among the higher-cost cancer medicines available. Final cost depends on body weight-based dosing, number of vials, hospital and infusion charges, insurance, and access programmes.
| India | Access is expanding following CDSCO approval. Branded Enhertu cost in India is significant and varies by centre, weight-based dosing, and number of vials. Government hospital access may differ from private oncology centres. Patient assistance options should be explored directly with AstraZeneca India. CancerFax can help patients navigate current access and cost-reduction pathways. |
| China | China has NMPA approvals for multiple Enhertu indications. Cost in China's public hospital system may differ from private centres. National Reimbursement Drug List (NRDL) inclusion discussions are ongoing and status changes rapidly — verify current reimbursement status with your China hospital or through CancerFax. |
| USA | Enhertu is broadly FDA-approved and available through oncology centres. List price is high, but most patients access it through insurance. Patient assistance programmes are available through AstraZeneca's US patient support programmes for eligible patients without adequate insurance coverage. |
| Europe / UK | Enhertu is EMA-authorized and available in multiple European countries. NHS access in the UK depends on NICE or SMC approval by indication. Other European countries have varying national reimbursement coverage — access and timing depend on country-level health technology assessment decisions. |
| Singapore / South Korea / Japan | Enhertu is approved and available in Japan (joint Daiichi Sankyo/AstraZeneca home market), South Korea, and Singapore. Each country has its own regulatory approval and insurance coverage structure. Access through specialist cancer centres is typically available. |
| Southeast Asia / MENA / Rest of world | Access varies significantly by country. In markets without local approval, compassionate use, named patient access, or clinical trial access may be routes available. CancerFax can help assess current options for patients in India, Southeast Asia, Russia, CIS, and MENA regions. |
Availability of Trastuzumab Deruxtecan globally
Enhertu is available in most major markets through regulatory approvals, with expanding access in India, China, and international oncology centres. Availability by indication varies by country.
India
CDSCO-approved for HER2-positive cancers including breast cancer. Available at specialist cancer hospitals in major cities. Pricing varies by centre and weight-based dosing. CancerFax can help navigate current access and cost options.
China
NMPA approvals for HER2-positive/low breast cancer, HER2-positive gastric/GEJ cancer, and HER2-mutant NSCLC. Available at National Cancer Center Beijing, Fudan University Shanghai Cancer Center, and major oncology centres.
USA
Broad FDA approval across all major HER2-related indications. Available through oncology centres nationwide. Patient assistance programmes are available from AstraZeneca for eligible patients with inadequate insurance coverage.
Europe
EMA-authorized with risk minimization materials for ILD/pneumonitis. Available at specialist oncology centres across EU, UK, and Switzerland. Country-level NHS or national insurance reimbursement varies — verify with your oncology centre.
Japan
Japan is a home market for Daiichi Sankyo, co-developer of Enhertu. First approved in Japan with broad indication coverage. Available through specialist cancer hospitals under Japan's health insurance system.
South Korea / Singapore
Available through specialist cancer hospitals in both markets under local regulatory approvals. Key access points for patients in Southeast Asia. CancerFax can assist patients from the region with referral and treatment navigation.
Trastuzumab Deruxtecan in current clinical trials
While Enhertu has multiple established indications, active research continues to explore new combinations, earlier treatment lines, new cancer types, and predictive biomarkers for response.
| DESTINY trial programme (ongoing) | The DESTINY-Breast, DESTINY-Gastric, DESTINY-Lung, and DESTINY-PanTumor series continues to generate data on Enhertu in new cancer types, earlier treatment lines, neoadjuvant settings, and new patient populations not yet covered by approved indications. |
| First-line breast cancer combinations | Trials exploring Enhertu in combination with checkpoint inhibitors, CDK4/6 inhibitors, and other targeted agents in first-line metastatic breast cancer settings, including both HER2-positive and HER2-low populations. |
| Neoadjuvant and early breast cancer settings | Studies evaluating T-DXd in the neoadjuvant or early breast cancer setting to assess whether earlier use in patients with high HER2 expression or HER2-low disease could improve long-term outcomes. |
| New HER2-positive solid tumor types | Ongoing basket trial work identifying additional cancer types where HER2 IHC 3+ positivity may predict response to Enhertu — including colorectal, biliary tract, endometrial, bladder, and other rare solid tumors. |
| Resistance mechanism research and next-generation ADCs | Translational studies characterizing mechanisms of acquired resistance to Enhertu, with the goal of identifying companion biomarkers and designing rational next-line treatment strategies using novel ADCs or bispecific antibodies. |
| HER2-mutant cancers beyond NSCLC | Research exploring the role of HER2/ERBB2 mutations as a targetable driver in other solid tumor types including colorectal cancer, biliary tract cancer, and rare HER2-mutant solid tumors not yet covered by current approvals. |
Your treatment journey with Trastuzumab Deruxtecan
Step 1 — Diagnosis and HER2 testing
Step 2 — Oncology consultation and eligibility review
Step 3 — Baseline investigations
Step 4 — First infusion and early monitoring
Step 5 — Ongoing infusion cycles and response assessment
Step 6 — Managing side effects and dose adjustments
Step 7 — Long-term treatment continuation or change
Questions to ask your oncologist about Trastuzumab Deruxtecan
- Is my cancer HER2-positive, HER2-low, HER2-ultralow, or HER2-mutant — and what does that mean for Enhertu eligibility?
- Have I received the required prior treatments that Enhertu's approval depends on?
- What is the most serious risk I should watch for with Enhertu, and how will we monitor for it?
- How will you monitor my heart function during treatment?
- What benefit can I realistically expect in my specific cancer type and at my stage?
- What happens if my scans show the cancer is progressing on Enhertu?
- Are there clinical trials I should consider at this stage?
- Can I access Enhertu in India or China, and how does the cost compare?
How CancerFax supports Trastuzumab Deruxtecan patients
CancerFax helps patients and families navigate HER2 testing results, understand Enhertu eligibility, access specialist oncology opinions, and explore treatment options in India, China, and internationally.
| HER2 report review | Upload your IHC, FISH/ISH, or NGS report and treatment history — our oncology team will review the results and explain what they mean for Enhertu eligibility, HER2 classification, and next steps. |
| Specialist connection | We connect patients with medical oncologists experienced in HER2-directed therapy and ADCs for breast, gastric, lung, and HER2-positive solid tumor cases in India and internationally. |
| Second opinion coordination | If you are uncertain about your HER2 testing result, treatment plan, or whether Enhertu is appropriate for your case, CancerFax arranges structured second opinions with senior oncologists in India and China. |
| India access guidance | We help patients check current Enhertu availability in India, identify appropriate specialist cancer centres, and navigate patient assistance or cost-reduction options available through AstraZeneca India. |
| China hospital access | CancerFax has established connections with leading cancer hospitals in China — including Fudan University Shanghai Cancer Center and National Cancer Center Beijing — and can help patients explore Enhertu access, trial options, and ADC treatment pathways. |
| Clinical trial matching | We identify active clinical trials involving Enhertu, next-generation ADCs, bispecific antibodies, and HER2-targeted combination therapies across India, China, Singapore, and international centres for patients who may benefit from trial access. |
Frequently asked questions about Trastuzumab Deruxtecan
Common questions from patients and caregivers about Enhertu
Trastuzumab deruxtecan (Enhertu / T-DXd) is used for selected patients with HER2-positive, HER2-low, HER2-ultralow, or HER2-mutant cancers. FDA-approved indications include HER2-positive and HER2-low or HER2-ultralow metastatic breast cancer, HER2-positive locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma, HER2-mutant unresectable or metastatic non-small cell lung cancer, and selected HER2-positive IHC 3+ unresectable or metastatic solid tumors after prior systemic treatment.
Enhertu is an antibody-drug conjugate (ADC), which means it is a form of targeted therapy that also carries a chemotherapy-like payload. The trastuzumab antibody part guides the drug toward HER2-expressing cancer cells, and once inside the cell, it releases DXd, a topoisomerase I inhibitor that damages cancer cell DNA. It is more targeted than traditional chemotherapy but still carries significant side effects that need careful oncology monitoring.
Interstitial lung disease (ILD) and pneumonitis are among the most serious risks with Enhertu, and some cases have been fatal. Patients must report any new or worsening cough, breathlessness, fever, or chest tightness to their oncologist immediately. The FDA label states that Enhertu should be permanently discontinued in patients who develop Grade 2 or higher ILD or pneumonitis. Early detection is critical — do not delay reporting any breathing symptoms.
Yes, HER2 testing is essential and the type of test depends on your cancer. For breast cancer, IHC and ISH or FISH testing determines HER2-positive, HER2-low, or HER2-ultralow status. For lung cancer, an activating HER2 or ERBB2 mutation detected by NGS or an FDA-approved molecular test is required. For gastric cancer, HER2 IHC or ISH testing is needed, and the FDA label recommends reassessing HER2 status after prior trastuzumab-based therapy. Testing must be done at a validated laboratory before treatment starts.
Yes. HER2-low breast cancer, defined as IHC 1+ or IHC 2+ with ISH-negative, was previously considered HER2-negative and ineligible for HER2-directed therapy. The DESTINY-Breast04 trial showed that trastuzumab deruxtecan significantly improved outcomes in HER2-low metastatic breast cancer compared with physician's choice chemotherapy. The FDA label now includes HER2-low and HER2-ultralow metastatic breast cancer indications for Enhertu.
Yes, access to Enhertu in India is expanding. AstraZeneca Pharma India has received CDSCO approval to import, market, and distribute trastuzumab deruxtecan (Enhertu) in India, including for HER2-positive solid tumors and HER2-positive breast cancer settings. Cost can be significant and varies by weight-based dosing, hospital, and insurance coverage. CancerFax can help patients check current availability, access options, and estimated costs in India.
Yes. China has become an important access market for Enhertu, with multiple NMPA approvals across HER2-positive and HER2-low breast cancer, HER2-positive gastric or GEJ cancer, and HER2-mutant NSCLC settings. China's rapid expansion of ADC access has made it one of the more accessible markets for trastuzumab deruxtecan in Asia. CancerFax can help patients explore hospital options, current approval status, and cost navigation in China.
Enhertu is given as an intravenous (IV) infusion in a hospital, oncology daycare, or infusion centre. It is not a tablet. The most commonly used dose is 5.4 mg per kilogram for breast cancer, NSCLC, and HER2-positive IHC 3+ solid tumors, and 6.4 mg per kilogram for HER2-positive gastric cancer, given once every 3 weeks. The exact dose, schedule, and number of cycles are decided by the treating oncologist based on cancer type, weight, and organ function.
Yes. In HER2-positive metastatic breast cancer, trastuzumab deruxtecan is commonly used after prior anti-HER2 therapy. The DESTINY-Breast03 trial showed superior outcomes for Enhertu compared with T-DM1 (ado-trastuzumab emtansine) in previously treated HER2-positive metastatic breast cancer. In HER2-positive gastric cancer, it is used after prior trastuzumab-based therapy. Your oncologist will review your full treatment history to determine when Enhertu is most appropriate.
No. The FDA label includes a boxed warning for embryo-fetal toxicity. Enhertu can cause serious harm to an unborn baby and must not be used during pregnancy. Women of childbearing potential must use effective contraception during treatment and for a period after the last dose as advised by their oncologist. Patients who become pregnant during treatment should inform their doctor immediately. Breastfeeding is also not recommended during and after treatment.
If Enhertu stops controlling the cancer, the oncologist will typically arrange repeat imaging (CT, PET-CT, or MRI) to confirm progression, and may recommend a repeat biopsy or liquid biopsy to check for new mutations or changes in HER2 expression. NGS testing may identify alternative targets. Options may include a change of systemic therapy, enrolment in a clinical trial studying newer ADCs or bispecific antibodies, or a specialist second opinion to explore advanced options in India, China, or internationally.
Yes, selected patients with unresectable or metastatic non-small cell lung cancer (NSCLC) who have activating HER2 or ERBB2 mutations may be eligible for Enhertu after prior systemic therapy. In lung cancer, the key test is a molecular test such as NGS to detect the HER2 or ERBB2 mutation, not IHC or FISH as used in breast cancer. The DESTINY-Lung02 trial demonstrated durable responses in this patient group. Eligibility must be confirmed by a specialist oncologist with the molecular test result.