FOLFIRI Administration
The standard FOLFIRI regimen consists of irinotecan 180 mg/m² IV over 30-90 minutes on day 1, leucovorin 400 mg/m² IV over 2 hours on day 1 (or 200 mg/m² if using racemic leucovorin), 5-FU 400 mg/m² IV bolus on day 1, followed by 5-FU 2400 mg/m² as a continuous infusion over 46-48 hours, repeated every 2 weeks 1.
Dosing Schedule
Standard Regimen Components
- Irinotecan: 180 mg/m² IV infused over 30-90 minutes on day 1
- Leucovorin: 400 mg/m² IV over 2 hours on day 1 (equivalent to levoleucovorin 200 mg/m²)
- 5-Fluorouracil:
- Bolus: 400 mg/m² IV on day 1
- Continuous infusion: 1200 mg/m²/day × 2 days (total 2400 mg/m² over 46-48 hours)
- Cycle frequency: Every 2 weeks 1
Critical Ordering Safety
Order chemotherapy in 24-hour units (1200 mg/m²/day) rather than cumulative doses (2400 mg/m² over 48 hours) to minimize medication errors 2, 1. This is an NCCN-recommended safety practice.
Alternative FOLFIRI Schedules
An older two-day schedule exists but is less commonly used:
- Irinotecan 180 mg/m² day 1
- Leucovorin 200 mg/m² days 1 and 2
- 5-FU 400 mg/m² bolus followed by 600 mg/m² over 22 hours on days 1 and 2
- Repeat every 2 weeks 2
Dose Modifications
Starting Dose Reductions
Consider reducing the starting dose by one level for patients with:
- Prior pelvic/abdominal radiotherapy
- Performance status of 2
- Elevated bilirubin levels
- UGT1A1 polymorphisms: Reduce starting dose by at least one level for patients homozygous for UGT1A1*28 or *6 alleles, or compound heterozygous (*6/*28) 3
Toxicity-Based Modifications
Withhold FOLFIRI for:
- Grade 3-4 diarrhea
- Grade 3-4 mucositis
- Grade 4 neutropenia
- Grade 2-3 hand-foot syndrome
- Cardiac toxicity (angina, MI, arrhythmia, heart failure)
- Hyperammonemic encephalopathy
- Neurological toxicity (cerebellar syndrome, confusion, ataxia, visual disturbances) 4
Resume at reduced dose once toxicity resolves to ≤ Grade 1 for diarrhea, mucositis, myelosuppression, or hand-foot syndrome. Do not resume after cardiac, encephalopathic, or severe neurological events 4.
Specific Dose Adjustment Guidelines
For neutropenia during treatment:
- Grade 2 (1000-1499/mm³): Reduce by 1 dose level
- Grade 3 (500-999/mm³): Omit dose until ≤ Grade 2, then reduce by 1 level
- Grade 4 (<500/mm³): Omit dose until ≤ Grade 2, then reduce by 2 levels 3
For diarrhea:
- Grade 2 (4-6 stools/day above baseline): Omit dose until baseline, maintain dose level at next cycle
- Grade 3 (7-9 stools/day): Omit until baseline, reduce by 1 level
- Grade 4 (≥10 stools/day): Omit until baseline, reduce by 2 levels 3
Monitoring Requirements
Pre-Treatment Assessment
Before each cycle, verify:
- Absolute neutrophil count ≥1500/mm³
- Platelet count ≥100,000/mm³
- Resolution of treatment-related diarrhea (no antidiarrheal medications needed for ≥24 hours)
- Bilirubin levels (use caution with elevated levels; dosing cannot be recommended for bilirubin >2 mg/dL) 2, 3
Cycle Delays
Delay treatment 1-2 weeks if counts have not recovered or diarrhea persists. Consider discontinuing therapy if recovery does not occur after a 2-week delay 3.
UGT1A1 Testing
While commercially available, guidelines for routine clinical use have not been established 2. However, if known, use results to guide initial dosing as noted above.
Premedication
Administer antiemetic agents at least 30 minutes before FOLFIRI. The standard approach includes:
- Dexamethasone 10 mg IV
- 5-HT3 antagonist (ondansetron or granisetron) 3
Provide patients with an antiemetic regimen for home use to manage delayed nausea.
Combination Therapy Considerations
With Bevacizumab
Add bevacizumab 5 mg/kg IV on day 1, repeated every 2 weeks. Bevacizumab can be safely administered at 0.5 mg/kg/min (5 mg/kg over 10 minutes) 1.
With Cetuximab (RAS wild-type only)
- Loading dose: 400 mg/m² IV over 2 hours
- Maintenance: 250 mg/m² IV weekly, OR
- Alternative: 500 mg/m² IV every 2 weeks 1
With Panitumumab (RAS wild-type only)
6 mg/kg IV over 60 minutes on day 1, every 2 weeks 1
Common Pitfalls
Infusional 5-FU is strongly preferred over bolus regimens when combining with irinotecan 2. Bolus-only 5-FU regimens are inappropriate for combination with irinotecan or oxaliplatin.
Do not use EGFR inhibitors (cetuximab/panitumumab) in patients with RAS or BRAF mutations—they are ineffective and add toxicity 1.
Avoid switching between cetuximab and panitumumab after failure on one agent; no data support this practice 2, 1.
Monitor closely for neutropenia (occurs in 36-52% at Grade 3-4) and diarrhea (Grade 3-4 in 5-20% of patients) 5, 6, 7.