Recommended Dosage for Trastuzumab in HER2-Positive Breast and Gastric Cancer
For HER2-positive breast cancer and metastatic gastric cancer, trastuzumab should be administered either as a loading dose of 8 mg/kg IV followed by 6 mg/kg IV every 3 weeks, or as a loading dose of 4 mg/kg IV followed by 2 mg/kg IV weekly. 1
Dosing Regimens by Cancer Type
HER2-Positive Breast Cancer
Adjuvant Treatment Options:
- Weekly regimen: 4 mg/kg IV loading dose followed by 2 mg/kg IV weekly for 12 weeks (with paclitaxel or docetaxel) or 18 weeks (with docetaxel and carboplatin), then 6 mg/kg IV every 3 weeks to complete a total of 52 weeks of therapy 1
- Three-weekly regimen: 8 mg/kg IV loading dose followed by 6 mg/kg IV every 3 weeks for 52 weeks 1
Metastatic Breast Cancer:
- 4 mg/kg IV loading dose followed by 2 mg/kg IV weekly until disease progression 1
HER2-Positive Metastatic Gastric Cancer
- 8 mg/kg IV loading dose followed by 6 mg/kg IV every 3 weeks until disease progression 1
Administration Guidelines
- Trastuzumab must be administered as an intravenous infusion and should never be given as an IV push or bolus 1
- Initial loading dose should be administered over 90 minutes 1
- Subsequent maintenance doses can be administered over 30-90 minutes if the loading dose was well tolerated 1
- Do not substitute trastuzumab for or with ado-trastuzumab emtansine or fam-trastuzumab deruxtecan 1
Combination Therapy Considerations
- When used in combination with chemotherapy, trastuzumab should be administered with a taxane but should not be given concurrently with anthracyclines due to increased risk of cardiotoxicity 2, 3
- For TCH (docetaxel/carboplatin/trastuzumab) regimen, trastuzumab is given at 8 mg/kg IV loading dose followed by 6 mg/kg IV every 3 weeks 2
- For weekly TCH regimen, trastuzumab is given at 4 mg/kg IV loading dose followed by 2 mg/kg IV weekly 2
Monitoring and Safety Considerations
- Cardiac function should be assessed at baseline and monitored every 3 months during treatment due to potential cardiotoxicity 4, 5
- Patients with LVEF <50-55% should not receive trastuzumab 5
- Common adverse events include infusion-related reactions (fever, chills) which typically occur with the first dose 6
- Monitor for signs of cardiotoxicity, which is more common when trastuzumab is combined with anthracycline-based therapy 6
Duration of Treatment
- For adjuvant treatment of early breast cancer, the recommended duration is 1 year (52 weeks) 2, 3
- For metastatic breast cancer and gastric cancer, treatment continues until disease progression or unacceptable toxicity 1
Important Clinical Considerations
- Patient selection should be based on HER2 testing using FDA-approved tests by laboratories with demonstrated proficiency 1
- HER2-positive status is defined as IHC score of 3+ or FISH ratio >2.0 3
- Trastuzumab has shown significant improvements in disease-free survival and overall survival in HER2-positive breast cancer 7
- Higher-than-steady-state serum concentrations can be achieved with intensive loading regimens, which may maximize clinical benefit 8