AC Chemotherapy Administration Frequency
AC (Adriamycin/doxorubicin and Cyclophosphamide) chemotherapy is typically administered every 21 days (3 weeks) for 4 cycles in standard regimens. 1
Standard AC Regimen Details
The standard AC regimen consists of:
- Doxorubicin (Adriamycin): 60 mg/m² IV on day 1
- Cyclophosphamide: 600 mg/m² IV on day 1
- Cycled every 21 days for a total of 4 cycles 1
Alternative AC Administration Schedules
Dose-Dense AC
- Administered every 14 days (2 weeks) instead of every 21 days
- Same doses: Doxorubicin 60 mg/m² and Cyclophosphamide 600 mg/m²
- Requires growth factor support with filgrastim or pegfilgrastim
- Has shown improved outcomes in certain breast cancer patients 1, 2
Other AC Variations
- AC chemotherapy (standard schedule) followed by paclitaxel (either weekly for 12 weeks or every 3 weeks for 4 cycles) 1
- AC chemotherapy followed by docetaxel (100 mg/m² every 21 days for 4 cycles) 1
Clinical Considerations
Cardiac Monitoring
- LVEF assessment is recommended before starting AC chemotherapy due to potential cardiotoxicity of doxorubicin
- Dose-dense AC has not been associated with frequent short-term changes in LVEF 2
- Trastuzumab should not be given concurrently with anthracyclines due to increased cardiac toxicity risk 1
Toxicity Management
- Standard AC regimens may have higher rates of day 1 neutropenia (10%) compared to accelerated regimens with growth factor support (0%) 3
- Growth factor support (G-CSF) is mandatory for dose-dense AC regimens to prevent neutropenia 1, 3
Sequence with Other Therapies
- Chemotherapy and endocrine therapy should be given sequentially, with endocrine therapy after chemotherapy 1
- Radiation therapy should be administered after completion of AC chemotherapy 1
Common Pitfalls and Caveats
Failure to provide growth factor support with dose-dense regimens can lead to severe neutropenia and treatment delays
Cardiac monitoring is essential when using anthracycline-based regimens, particularly in patients with pre-existing cardiac risk factors
Drug interactions should be carefully monitored, as doxorubicin is metabolized through the CYP450 system
Cumulative dose limits for doxorubicin should be tracked to prevent cardiotoxicity (typically 450-480 mg/m² lifetime maximum)
Hydration protocols should be followed to reduce risk of hemorrhagic cystitis from cyclophosphamide
In conclusion, while standard AC chemotherapy is administered every 21 days for 4 cycles, dose-dense administration every 14 days with growth factor support has shown improved outcomes in certain breast cancer populations and may be preferred when rapid disease control is needed.