Ibrance Dose Modification for ANC 1.3 × 10³/mm³
Continue Ibrance at the current dose of 125 mg daily without modification, as an ANC of 1.3 × 10³/mm³ (1300/mm³) represents Grade 2 neutropenia, which does not require dose adjustment according to FDA labeling. 1
Grading and Management Algorithm
The FDA-approved dosing guidelines for Ibrance (palbociclib) specify clear thresholds for neutropenia management based on Common Terminology Criteria for Adverse Events (CTCAE) grading 1:
Current Clinical Scenario
- ANC 1.3 × 10³/mm³ = Grade 2 neutropenia (ANC 1000-1500/mm³) 1
- No dose adjustment required for Grade 1 or Grade 2 neutropenia 1
When to Hold Ibrance
Grade 3 neutropenia (ANC 500-1000/mm³): 1
- On Day 1 of cycle: Withhold Ibrance, repeat complete blood count within 1 week. When recovered to Grade ≤2, start next cycle at same dose 1
- On Day 15 of first 2 cycles: Continue current dose to complete cycle and recheck on Day 22. If Grade 4 on Day 22, follow Grade 4 guidelines 1
- Consider dose reduction only for prolonged (>1 week) recovery from Grade 3 or recurrent Grade 3 on Day 1 of subsequent cycles 1
Grade 3 neutropenia with fever ≥38.5°C and/or infection: 1
- Withhold Ibrance until recovery to Grade ≤2
- Resume at next lower dose (100 mg daily) 1
Grade 4 neutropenia (ANC <500/mm³): 1
- Withhold Ibrance until recovery to Grade ≤2
- Resume at next lower dose 1
Monitoring Requirements
For patients with Grade 1-2 neutropenia in first 6 cycles: 1
- Monitor complete blood counts prior to start of each cycle
- Check on Day 1 and Day 15 of first 2 cycles
- Monitor as clinically indicated 1
After 6 cycles with maximum Grade 1-2 neutropenia: 1
- Monitor complete blood counts every 3 months prior to beginning of cycle
- Continue monitoring as clinically indicated 1
Clinical Context from Research
Palbociclib-associated neutropenia differs substantially from chemotherapy-induced neutropenia 2:
- Median time to onset of any neutropenia: 15 days (range 12-700 days) 2
- Median time to Grade ≥3 neutropenia: 28 days (range 12-854 days) 2
- Median duration of each Grade ≥3 episode: 7 days 2
- Neutropenia is transient and manageable by dose modifications without compromising efficacy 2
Risk Factors for Severe Neutropenia
Important Caveats
Do not confuse with other tyrosine kinase inhibitors: The evidence provided includes management guidelines for CML therapies (imatinib, nilotinib, dasatinib), which have different neutropenia thresholds and are not applicable to palbociclib 3. Palbociclib is a CDK4/6 inhibitor for breast cancer with distinct hematologic toxicity profiles.
Dose reduction schedule if needed: 1
- Starting dose: 125 mg/day
- First reduction: 100 mg/day
- Second reduction: 75 mg/day
- If further reduction below 75 mg/day required: discontinue 1