Trastuzumab (Herceptin)
Anti-HER2 monoclonal antibody for HER2-positive breast and gastric cancer.
What is Trastuzumab?
What it targets
Trastuzumab targets the HER2 receptor (ErbB2). In HER2-positive cancers, excess HER2 protein drives rapid cancer cell growth and division.
Who it may help
Patients with confirmed HER2 overexpression (IHC 3+) or HER2 gene amplification (ISH/FISH) in breast, gastric, or GEJ cancer.
Why testing matters
HER2 testing by IHC and ISH/FISH confirms whether a tumor has the target trastuzumab is designed to block. Testing is required before treatment can be planned.
Which cancers can trastuzumab treat?
Trastuzumab is approved for HER2-positive cancers confirmed by validated IHC or ISH/FISH testing.
| HER2-positive early breast cancer (neoadjuvant) | Used with chemotherapy before surgery in eligible patients to shrink the tumor and improve the chance of achieving pathological complete response. |
| HER2-positive early breast cancer (adjuvant) | Given after surgery and chemotherapy to reduce the risk of cancer recurrence. Standard adjuvant therapy is typically one year of trastuzumab. |
| HER2-positive metastatic breast cancer | Used with chemotherapy or with pertuzumab and chemotherapy as first-line treatment, and in later lines after prior HER2-targeted therapy based on treatment history. |
| HER2-positive metastatic gastric cancer | Combined with chemotherapy for patients with confirmed HER2 overexpression. The ToGA trial established this as a standard approach in HER2-positive metastatic gastric adenocarcinoma. |
| HER2-positive gastroesophageal junction cancer | May be used in metastatic GEJ adenocarcinoma when HER2 positivity is confirmed by biopsy testing at an experienced pathology center. |
Are you eligible for trastuzumab?
Eligibility depends on confirmed HER2 status, cancer type, cardiac function, and overall health.
- HER2-positive confirmed by IHC 3+ or by ISH/FISH showing HER2 gene amplification
- Breast cancer diagnosis — early-stage (neoadjuvant or adjuvant) or metastatic HER2-positive
- Metastatic gastric or GEJ adenocarcinoma with confirmed HER2 overexpression
- Adequate cardiac function — LVEF within normal limits before starting treatment
- Adequate liver, kidney, and bone marrow function confirmed on baseline blood tests
- Not currently pregnant — trastuzumab can cause harm to an unborn baby
- Not breastfeeding during treatment and for at least 7 months after the last dose
- No known severe hypersensitivity to trastuzumab or murine proteins
How does trastuzumab work?
- HER2 receptor binding
- Blocking HER2-driven growth signals
- Immune system activation (ADCC)
- Slowing cancer cell division
- Enhancing chemotherapy effect
Trastuzumab was among the first targeted antibodies to prove that blocking a specific cancer driver protein could meaningfully improve patient outcomes.
Tests required before starting trastuzumab
These tests confirm HER2 eligibility, assess cardiac baseline, and guide the treatment plan.
| Biopsy and histopathology | Tissue diagnosis confirming cancer type is required before HER2 testing can be performed and a treatment plan developed. |
| HER2 testing by IHC | Immunohistochemistry measures HER2 protein expression on cancer cells. IHC 3+ is HER2-positive; IHC 2+ is borderline and requires further testing. |
| HER2 testing by ISH / FISH (confirmatory) | Required when IHC gives a borderline 2+ result. In situ hybridization confirms whether the HER2 gene is amplified and establishes definitive HER2 status. |
| ER and PR status (breast cancer) | Hormone receptor testing in breast cancer determines whether endocrine therapy should be added alongside trastuzumab. |
| Cardiac function — ECHO or MUGA scan | Measures baseline left ventricular ejection fraction (LVEF) before starting trastuzumab. Repeated during treatment — typically every 3 months. |
| Complete blood count (CBC) | Baseline white cell, red cell, and platelet counts. Repeated regularly during treatment, especially when combined with chemotherapy. |
| Liver function tests | Baseline liver function assessment before starting trastuzumab and chemotherapy combination. |
| Kidney function tests | Baseline kidney function required for overall safety assessment and dosing decisions. |
| Staging scans | CT, PET-CT, MRI, or bone scan depending on cancer stage. Establishes disease extent before treatment and provides the baseline for response assessment. |
How is trastuzumab given?
Trastuzumab is most commonly given as an intravenous infusion at a hospital or day-care oncology center. A subcutaneous formulation is available for breast cancer patients in some regions.
| Dosage — breast cancer IV (loading dose) | 8 mg/kg by IV infusion for the first dose (3-weekly schedule), or 4 mg/kg for the weekly schedule. |
| Dosage — breast cancer IV (maintenance) | 6 mg/kg every 3 weeks after the loading dose, or 2 mg/kg weekly. Schedule depends on the combination chemotherapy regimen. |
| Dosage — gastric or GEJ cancer (IV) | 8 mg/kg loading dose, then 6 mg/kg every 3 weeks, given in combination with chemotherapy. |
| Subcutaneous formulation (breast cancer) | Fixed dose of 600 mg SC every 3 weeks. Approved in some regions including Europe and parts of Asia. Takes minutes to administer vs. standard IV infusion. |
| First infusion monitoring | The first IV infusion is given slowly — usually over 90 minutes — with continuous monitoring for infusion reactions. Later infusions may be given over 30 minutes if the first is well tolerated. |
| Duration — adjuvant breast cancer | Typically 1 year of adjuvant trastuzumab after surgery and chemotherapy, approximately 18 cycles on a 3-weekly schedule. |
| Duration — metastatic disease | Treatment continues as long as cancer responds and side effects are manageable. Your oncologist will review continuation at each assessment. |
| Missed or delayed dose | Contact your oncology team immediately if an infusion is missed or delayed. Do not attempt to reschedule without medical guidance. |
Clinical evidence and benefits of trastuzumab
Trastuzumab has been studied in large randomized trials across HER2-positive breast cancer and gastric cancer, establishing it as a standard of care.
| Adjuvant breast cancer — reduced recurrence risk | Landmark trials including HERA, BCIRG 006, and NSABP B-31 demonstrated substantially reduced risk of cancer recurrence in HER2-positive early breast cancer compared to chemotherapy alone. |
| Neoadjuvant breast cancer — improved response | Adding trastuzumab to neoadjuvant chemotherapy significantly improves pathological complete response rates at surgery, which is associated with better long-term outcomes. |
| Metastatic breast cancer — improved disease control | Trastuzumab-based regimens produce meaningful improvements in progression-free and overall survival in HER2-positive metastatic breast cancer compared to chemotherapy alone. |
| HER2-positive gastric cancer — survival benefit | The ToGA trial demonstrated that adding trastuzumab to cisplatin-based chemotherapy significantly improved outcomes in patients with HER2-positive metastatic gastric or GEJ cancer. |
| Biosimilar equivalence | Multiple approved biosimilar trastuzumab products have demonstrated equivalent clinical outcomes to the original Herceptin in large equivalence trials, supporting broader patient access globally. |
Individual responses vary. These outcomes represent published clinical trial data and do not predict results for any individual patient.
Side effects of trastuzumab
Trastuzumab has a generally more targeted side effect profile than chemotherapy, but it carries important cardiac and infusion-related risks that require ongoing monitoring.
| Fever or chills during infusion | Common during or shortly after the first infusion. Usually managed with pre-medication and a slower infusion rate. Less frequent with subsequent doses. |
| Fatigue | Reported in many patients, particularly when combined with chemotherapy. Often manageable with rest and activity adjustment. |
| Nausea | More common when trastuzumab is given alongside chemotherapy. Anti-nausea medicines can help manage this effectively. |
| Diarrhea | May occur, especially in combination regimens. Hydration and dietary adjustments are usually sufficient. Report persistent diarrhea to your doctor. |
| Headache | Reported as a common side effect. Usually mild and manageable without treatment interruption. |
| Rash or skin changes | Skin reactions may occur. Report any new or worsening rash to your oncology team. |
| Cough | Respiratory symptoms including cough can occur during treatment. Persistent or worsening cough should be reported promptly. |
| Low blood counts (with chemotherapy) | Neutropenia, anemia, and thrombocytopenia are more common when trastuzumab is combined with chemotherapy. Regular CBC monitoring is required. |
| Muscle or joint pain | Arthralgias and myalgias may occur during treatment. Report significant or worsening pain to your oncology team. |
| Cardiac dysfunction — reduced LVEF | Trastuzumab can reduce the heart's pumping efficiency. Regular ECHO or MUGA monitoring is essential. Risk is increased with prior anthracycline chemotherapy. |
| Infusion reactions | Fever, chills, rash, or breathing difficulty during infusion — most often with the first dose. Nursing staff are present to manage reactions throughout. |
| Pulmonary toxicity | Rare but serious breathing problems including pneumonitis and pulmonary infiltrates may occur. Included in the FDA boxed warning. |
Contact your doctor immediately if you develop:
- Chest pain, shortness of breath, or difficulty breathing during or after infusion
- Swelling in the legs, ankles, or feet, or sudden unexplained weight gain
- Irregular heartbeat, palpitations, or feeling faint
- Severe rash, hives, or swelling of face, lips, or throat during infusion
- Fever above 38.5°C, chills, or other signs of serious infection
Safety precautions and important warnings
Tell your oncologist about all medicines, supplements, and herbal products before starting trastuzumab.
- Prior anthracycline chemotherapy (doxorubicin, epirubicin) significantly increases the cardiac risk of trastuzumab — report all prior treatments.
- Active heart disease or prior heart failure requires careful evaluation before starting trastuzumab.
- Trastuzumab causes embryo-fetal harm. Do not use during pregnancy. Use effective contraception during and for 7 months after the last dose.
- Do not breastfeed during treatment or for at least 7 months after the last trastuzumab dose.
- Pre-existing lung disease increases the risk of pulmonary toxicity — inform your oncologist of any breathing problems before starting.
- High blood pressure should be monitored and managed throughout trastuzumab treatment.
- Previous severe hypersensitivity to trastuzumab or murine proteins requires specialist assessment before re-challenge.
Trastuzumab combination treatments
Trastuzumab is rarely used as a single agent — it is almost always combined with chemotherapy or other HER2-targeted therapies for maximum benefit.
| Trastuzumab + Pertuzumab + chemotherapy | Dual HER2 blockade with trastuzumab and pertuzumab, combined with docetaxel, is standard first-line therapy for HER2-positive metastatic breast cancer and is also used in high-risk neoadjuvant early breast cancer (CLEOPATRA, NEOSPHERE). |
| Trastuzumab + Paclitaxel or Docetaxel | Standard taxane-based combinations for HER2-positive breast cancer in both early and metastatic settings. Carboplatin may be added in selected patients. |
| Trastuzumab + Cisplatin + 5-FU or Capecitabine | First-line treatment for HER2-positive metastatic gastric or GEJ cancer based on the ToGA trial. Chemotherapy backbone may be adapted based on patient fitness. |
| Trastuzumab + Endocrine therapy | In hormone receptor-positive, HER2-positive breast cancer, trastuzumab may be combined with endocrine therapy in selected settings, particularly when chemotherapy is not suitable. |
| Next-line options after trastuzumab failure | Trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan are antibody-drug conjugates used after prior trastuzumab. Availability and specific indications vary by country. |
If trastuzumab stops working
Resistance to trastuzumab can develop through several mechanisms. Identifying the cause guides next-line treatment decisions.
| HER2 loss or reduced expression | Some tumors reduce HER2 expression over time, limiting trastuzumab's ability to bind. Repeat biopsy may reveal HER2 heterogeneity or loss that developed after prior HER2-targeted therapy. |
| Downstream PIK3CA/PTEN pathway activation | Mutations in PIK3CA or loss of PTEN allow cancer cells to bypass HER2 blockade by activating downstream growth signals independently of HER2, making continued trastuzumab less effective. |
| Bypass signaling via other receptors | Upregulation of other growth receptors such as EGFR, HER3, or MET allows cancer cells to continue proliferating despite HER2 blockade, requiring a change in treatment strategy. |
| Next-line options after trastuzumab failure | Options include T-DM1, trastuzumab deruxtecan, lapatinib-based combinations, neratinib, tucatinib, and clinical trials. Second opinion and molecular profiling are recommended. |
Cost of trastuzumab by country
Biosimilar trastuzumab has significantly reduced treatment costs in many countries, though the original Herceptin brand remains available globally.
| India | Biosimilar trastuzumab is available from several Indian manufacturers at substantially lower cost than the original Herceptin. Patient assistance programs may also be available through hospital networks and oncologist coordination. CancerFax can help estimate current costs. |
| USA | Original Herceptin is expensive; multiple FDA-approved biosimilars now available at reduced cost. The Genentech HARBOR Access Program may offer assistance to eligible uninsured or underinsured patients. Insurance coverage is central to access planning. |
| UK / Europe | Covered by the NHS for eligible patients in the UK. Biosimilars are widely used across European health systems, significantly reducing trastuzumab costs compared to the branded originator. |
| China | Available at major oncology centers including Fudan University Shanghai Cancer Center. Biosimilar versions are on China's national reimbursement drug list. CancerFax can assist international patients with cost estimation and hospital coordination. |
| Singapore / South Korea | Available at leading cancer centers. South Korea has domestic biosimilar manufacturing. Singapore's major hospitals offer trastuzumab infusions. Insurance coverage and out-of-pocket costs vary by plan and hospital. |
Availability of trastuzumab globally
Trastuzumab and its biosimilars are available in most major oncology markets. Multiple biosimilar approvals have expanded access and reduced costs worldwide.
India
Multiple biosimilar trastuzumab products from Indian manufacturers make treatment more affordable. Available at major oncology hospitals and cancer centers across India. Patient assistance programs may further reduce costs for eligible patients.
China
Available at leading cancer hospitals including Fudan University Shanghai Cancer Center. Biosimilar versions are reimbursed on China's national drug list. CancerFax supports international patients seeking trastuzumab-based treatment in China.
USA
FDA-approved since 1998. Multiple biosimilars now approved and available at major infusion centers. Insurance and manufacturer assistance programs can offset costs. Original Herceptin also remains available at major oncology centers.
UK / Europe
EMA-approved. NHS-funded for eligible patients in the UK. Biosimilars are widely available across EU health systems, where national insurance typically covers trastuzumab for eligible breast and gastric cancer patients.
South Korea / Singapore
Widely available at major cancer centers. South Korea has domestic biosimilar manufacturing. Singapore's National Cancer Centre and private hospitals offer trastuzumab infusions. Insurance coverage and self-pay costs vary by plan.
Trastuzumab in current clinical trials
Active research programs continue to expand trastuzumab's role — from new patient populations to novel combinations and resistance strategies.
| HER2-low and HER2-mutant tumors | Trials are evaluating whether patients with lower HER2 expression or HER2 mutations can benefit from trastuzumab-based or ADC-based regimens, including trastuzumab deruxtecan in HER2-low breast cancer. |
| New HER2-targeted combination regimens | Studies combining trastuzumab with checkpoint inhibitors, CDK4/6 inhibitors, and novel agents are underway to improve outcomes in both early and metastatic HER2-positive breast cancer settings. |
| Extended adjuvant and de-escalation strategies | Trials investigating optimal adjuvant trastuzumab duration, de-escalation approaches for low-risk patients, and whether neratinib after trastuzumab provides additional benefit. |
| Resistance mechanisms and second-line strategies | Research programs studying why trastuzumab resistance develops and which biomarkers predict who will benefit most from second-line HER2-targeted therapies including T-DM1 and trastuzumab deruxtecan. |
Your treatment journey with trastuzumab
Diagnosis and biopsy
HER2 testing and staging
Cardiac assessment
Treatment planning consultation
First trastuzumab infusion
Early monitoring (first 3 months)
Response assessment
Completion or next-line decisions
Questions to ask your oncologist about trastuzumab
- Is my cancer confirmed HER2-positive, and which test was used — IHC or FISH?
- Will I need a heart test before and during trastuzumab treatment?
- How long will I receive trastuzumab?
- Will I also receive pertuzumab alongside trastuzumab?
- Is a biosimilar trastuzumab available, and is it as effective as Herceptin?
- What heart symptoms should I watch for and report immediately?
- Can I receive trastuzumab while pregnant or planning a pregnancy?
- What are my options if trastuzumab stops working?
- Is subcutaneous trastuzumab available in my country?
- What will trastuzumab treatment cost, and how can I access support?
How CancerFax supports trastuzumab patients
CancerFax helps HER2-positive cancer patients navigate treatment decisions, understand their test results, and access trastuzumab-based care across India, China, and other international oncology centers.
| Report review | Upload your HER2 IHC and FISH/ISH reports, staging scans, and biopsy results — our oncology team will review and explain what they mean for your trastuzumab eligibility and next steps. |
| Specialist connection | We connect patients with oncologists experienced in HER2-positive breast cancer and gastric cancer treatment in India, China, Singapore, and other leading oncology centers globally. |
| Cost and access navigation | We help patients identify legitimate biosimilar trastuzumab access channels, estimate treatment costs by country, and navigate patient assistance programs available through hospitals and manufacturers. |
| Second opinion coordination | If you are uncertain about your HER2 result, your treatment plan, or your options after trastuzumab failure, CancerFax arranges a specialist second opinion with an experienced oncologist. |
| Clinical trial matching | We explore trastuzumab combination trial opportunities in India, China, and other oncology research centers for eligible HER2-positive patients who may benefit from newer regimens. |
| International coordination | For patients seeking trastuzumab-based treatment outside their home country, CancerFax manages hospital liaison, medical record review, translation support, and treatment logistics. |
Frequently asked questions about trastuzumab
Common questions from HER2-positive cancer patients and caregivers
Trastuzumab is a targeted therapy — a monoclonal antibody that specifically binds to the HER2 protein on cancer cells. Unlike chemotherapy, which broadly affects all fast-dividing cells, trastuzumab works by blocking the HER2 receptor that drives cancer growth in HER2-positive tumors. It is given by infusion rather than as an oral tablet, and its side effect profile is generally more targeted than standard chemotherapy.
HER2 status is determined by testing a sample of your tumor tissue. IHC testing measures how much HER2 protein is on the cancer cells — a score of 3+ is considered HER2-positive. A score of 2+ is borderline and requires confirmation by ISH or FISH testing, which checks whether the HER2 gene is amplified. Your oncologist will explain your specific result and what it means for treatment options.
Treatment duration depends on the setting. In adjuvant early breast cancer, trastuzumab is typically given for one year (around 18 cycles on a 3-weekly schedule). In the neoadjuvant setting, it continues through pre-surgery treatment and usually extends after surgery. For metastatic disease, treatment continues as long as the cancer responds and side effects are manageable. Your oncologist will advise your specific plan.
Trastuzumab can reduce the heart's pumping efficiency (left ventricular ejection fraction) and, in some cases, cause cardiac dysfunction or heart failure. This risk is higher in patients who have previously received anthracycline chemotherapy such as doxorubicin or epirubicin. Regular heart monitoring with ECHO or MUGA scan is standard throughout treatment. Report any chest pain, shortness of breath, or leg swelling to your doctor immediately.
Yes — biosimilar trastuzumab products have been approved by the FDA, EMA, and other regulators after rigorous equivalence testing demonstrating they are equivalent to the original Herceptin in efficacy, safety, and quality. They contain the same active antibody at equivalent doses and have been confirmed in large clinical equivalence trials. Your oncologist can advise on which product is available and appropriate for your country and setting.
No — trastuzumab carries a boxed warning for embryo-fetal toxicity. It must not be used during pregnancy as it can cause serious harm to the developing baby. Women of childbearing potential must use effective contraception during treatment and for at least 7 months after the last dose. If you are planning a pregnancy after completing treatment, discuss timing carefully with your oncologist and a reproductive specialist.
If cancer progresses on or after trastuzumab, options may include antibody-drug conjugates such as trastuzumab emtansine (T-DM1) or trastuzumab deruxtecan, other HER2-targeted therapies, or clinical trial participation. Your oncologist may also recommend a repeat biopsy or liquid biopsy to understand the resistance mechanism. CancerFax can help arrange a specialist second opinion if you would like another perspective on next-line options.
A subcutaneous formulation of trastuzumab (fixed dose 600 mg every 3 weeks) is approved in many regions including Europe and parts of Asia for breast cancer treatment. It is administered as a short injection under the skin and takes only a few minutes compared to a standard IV infusion. Not all hospitals or countries offer this option. Ask your oncologist or oncology nurse whether the subcutaneous formulation is available in your setting.