Trastuzumab is NOT a Proton Pump Inhibitor
Trastuzumab is a humanized monoclonal antibody targeted against the HER2 receptor, used exclusively for treating HER2-positive breast cancer—it has absolutely no relationship to proton pump inhibitors, which are gastric acid-suppressing medications like omeprazole or pantoprazole. 1, 2
What Trastuzumab Actually Is
Trastuzumab is a targeted cancer therapy that binds with high affinity to the extracellular domain of the HER2 (human epidermal growth factor receptor 2) protein, which is overexpressed in 15-30% of breast cancers 1, 3
It functions as an IgG1 humanized monoclonal antibody administered by intravenous infusion, typically on a weekly or three-weekly schedule 2
The mechanism of action involves inhibiting proliferation of tumor cells that overexpress HER2, not suppressing gastric acid production 1, 3
Clinical Indications for Trastuzumab
Patient selection is based on HER2 protein overexpression or gene amplification, defined as IHC score of 3+ or FISH ratio >2.0 4, 5
Trastuzumab plus chemotherapy is recommended for all patients with HER2-positive, node-positive breast cancer and for HER2-positive, node-negative breast cancer >1 cm 5
The standard duration of adjuvant trastuzumab treatment is 1 year with regular cardiac function assessments 4, 5
Key Treatment Principles
Trastuzumab should be administered concurrently with taxanes (paclitaxel or docetaxel), NOT with anthracyclines, due to significant cardiotoxicity risk when combined with anthracyclines 5
Preferred regimens include AC (doxorubicin/cyclophosphamide) followed by paclitaxel + trastuzumab, or TCH (docetaxel/carboplatin/trastuzumab) 5, 4
For patients at higher cardiac risk, docetaxel-carboplatin-trastuzumab demonstrates less cardiotoxicity than anthracycline-containing regimens 5
Critical Safety Considerations
Cardiac dysfunction is the primary concern, with symptomatic or asymptomatic cardiac events occurring in 27% when combined with anthracyclines, 13% with paclitaxel, and 4.7% as monotherapy 1
Baseline cardiac function (LVEF) must be assessed prior to treatment with periodic monitoring throughout therapy 6
The cardiac effects are often at least partly reversible, but require careful monitoring 2, 7