The "7+3" Regimen Represents ONE Induction Cycle
The 7+3 regimen (7 days of continuous cytarabine plus 3 days of anthracycline) constitutes a single induction cycle, though patients may receive a second cycle if they have residual disease after the first cycle. 1, 2
Standard Induction Approach
The standard "7+3" induction consists of:
- Cytarabine: 100-200 mg/m² continuous IV infusion for 7 days
- Anthracycline: Daunorubicin 60-90 mg/m² (or idarubicin 10-12 mg/m²) for 3 days
This represents one cycle of induction therapy 1, 2.
When a Second Cycle is Given
After the first cycle, bone marrow assessment should be performed 14-21 days after starting therapy 3. A second induction cycle is administered only if:
- Significant residual disease is present (>5% blasts) without hypoplasia
- There is >50% cytoreduction but persistent residual blasts
- The marrow shows blast persistence rather than complete remission 3
The second cycle may use:
- The same 7+3 regimen (with reduced anthracycline dose if daunorubicin 90 mg/m² was used initially—reduce to 45 mg/m² for reinduction) 4, 3
- Escalation to intermediate-dose cytarabine (1.5-3 g/m² every 12 hours for 6 days) 3
- Alternative regimens like FLAG-Ida 5
Critical Distinction
Most patients (60-80% of younger adults) achieve complete remission after ONE cycle of 7+3 1, 2. The decision to give a second cycle is based on response assessment, not a predetermined plan. This differs fundamentally from consolidation therapy, which consists of multiple planned cycles after achieving remission.
Common Pitfall
Do not confuse induction cycles with consolidation cycles. After achieving CR with 1-2 induction cycles, patients then proceed to consolidation therapy, which typically involves 3-4 cycles of high-dose cytarabine or other intensive regimens 2. The "7+3" terminology specifically refers to the induction phase, not the total treatment course.