AC-THP Regimen

Indication:

• Neoadjuvant or adjuvant treatment of HER2-positive early-stage or locally advanced breast cancer.
• Often used in higher-risk disease when anthracyclines are indicated.

Regimen Components & Schedule

1. AC Phase (Anthracycline + Cyclophosphamide)

• Doxorubicin: 60 mg/m² IV day 1
• Cyclophosphamide: 600 mg/m² IV day 1
• Cycle length: 21 days × 4 cycles
• Support: Standard antiemetics; consider G-CSF if high risk for neutropenia

2. THP Phase (Taxane + HER2-targeted therapy)

• Paclitaxel: 80 mg/m² IV weekly × 12 weeks OR Docetaxel 75 mg/m² IV q3w × 4 cycles
• Trastuzumab:
  • Loading: 8 mg/kg IV day 1, then 6 mg/kg IV q3w (if using docetaxel)
  • Or weekly: 4 mg/kg loading, then 2 mg/kg weekly (if using paclitaxel)
• Pertuzumab:
  • Loading: 840 mg IV day 1, then 420 mg IV q3w
• Duration of HER2 therapy: Complete 1 year of trastuzumab ± pertuzumab

Key Pharmacist Notes

• Cardiac monitoring: Baseline LVEF (echocardiogram or MUGA) before trastuzumab/pertuzumab; repeat q3 months during therapy.
• Infusion reactions: HER2-targeted agents can cause chills, fever — premedicate if needed and monitor closely.
• Anthracycline toxicity: Cumulative doxorubicin dose should not exceed 450–550 mg/m²; monitor for cardiotoxicity and myelosuppression.
• Taxane hypersensitivity: Premedicate paclitaxel with dexamethasone, H1/H2 blockers; docetaxel with dexamethasone for edema prevention.
• HER2-targeted therapy sequencing: Do not give trastuzumab/pertuzumab concurrently with anthracyclines due to additive cardiotoxicity risk — start HER2 agents in the taxane phase.
• Supportive care: Anti-emetics for AC (high emetic risk), growth factor support if indicated, neuropathy monitoring for taxanes.