What is the AC (Adriamycin (doxorubicin) and Cytoxan (cyclophosphamide)) regimen for breast cancer treatment?

From the Guidelines

The AC regimen for breast cancer treatment consists of Adriamycin (doxorubicin) and Cytoxan (cyclophosphamide) administered intravenously every 2-3 weeks for a total of 4 cycles, with standard dosing being doxorubicin 60 mg/m² and cyclophosphamide 600 mg/m² per cycle, as recommended by the most recent guidelines 1.

Key Components of the AC Regimen

• The regimen typically takes 2-3 months to complete, depending on whether it's given on a dose-dense schedule (every 2 weeks) or standard schedule (every 3 weeks) 1.
• The dose-dense schedule requires growth factor support with medications like filgrastim to prevent severe neutropenia 1.
• Common side effects include hair loss, nausea, vomiting, fatigue, risk of infection, and potential cardiac toxicity from doxorubicin 1.
• Patients should maintain adequate hydration, especially after cyclophosphamide administration, to protect the bladder 1.

Considerations for High-Risk Breast Cancers

• AC may be followed by a taxane (paclitaxel or docetaxel) in sequence for higher-risk breast cancers 1.
• This combination works by different mechanisms - doxorubicin intercalates DNA and inhibits topoisomerase II while cyclophosphamide is an alkylating agent that cross-links DNA, both disrupting cancer cell division and promoting cell death 1.

Recent Guidelines and Recommendations

• The most recent guidelines from 2024 recommend the use of the AC regimen as a standard treatment option for breast cancer, with considerations for dose-dense scheduling and taxane sequencing 1.
• Other studies have also supported the use of the AC regimen, with some variations in dosing and scheduling 1.

From the Research

AC Regimen for Breast Cancer Treatment

The AC regimen, which consists of Adriamycin (doxorubicin) and Cytoxan (cyclophosphamide), is a commonly used chemotherapy treatment for breast cancer.

• The regimen has been established as a standard therapy for breast cancer, with four cycles of AC being accepted as the standard chemotherapy in breast cancer 2.
• The AC regimen is typically administered through bolus intravenous infusion for 30 minutes to one hour, although continuous infusion schedules of doxorubicin for 72 to 96 hours have been reported to reduce the incidence of cardiac toxicity somewhat 3.

Efficacy of the AC Regimen

The efficacy of the AC regimen has been demonstrated in several studies, including:

• A randomized trial that showed four cycles of AC to be effective in node-positive patients with breast cancer, with a significant improvement in disease-free survival and overall survival when compared to AC alone 2.
• A study that found the AC regimen to be superior to the CMF (cyclophosphamide, methotrexate, and fluorouracil) regimen in terms of disease-free survival and overall survival in patients with operable breast cancer 4.
• A retrospective analysis of 200 consecutive patients treated with the AC regimen followed by weekly paclitaxel, which showed a high efficacy and acceptable toxicity, with a median event-free survival and overall survival of 10.85 years and 12.61 years, respectively 5.

Administration and Toxicity

The AC regimen is typically administered every 3 weeks for four cycles, although dose-dense schedules have also been used 5.

• The toxicity of the AC regimen is generally manageable, with common side effects including alopecia, emesis, mucositis, and cardiotoxicity 3, 4.
• The use of continuous infusion schedules of doxorubicin may help reduce the incidence of cardiac toxicity, although this approach is not widespread due to concerns over compromising antitumor efficacy and logistical issues 3.