FOLFIRI ± bevacizumab or anti-EGFR antibody

Irinotecan-based doublet for metastatic colorectal cancer, with the biologic chosen by RAS status and tumour sidedness

For clinicians and students · Regimen tutorial · Colorectal cancer · 10 min read · last reviewed September 30, 2026

Overview

FOLFIRI swaps oxaliplatin for irinotecan, a topoisomerase I inhibitor. Irinotecan is a prodrug activated to SN-38 and inactivated by glucuronidation through UGT1A1. FOLFIRI and FOLFOX are equally effective first-line doublets in metastatic colorectal cancer. Which to use depends mainly on toxicity: neuropathy with FOLFOX, versus diarrhea and alopecia with FOLFIRI. A biologic is usually added, and choosing it is a biomarker decision:

Before any anti-EGFR decision, check extended RAS status (KRAS and NRAS exons 2–4), BRAF, MMR/MSI and ideally HER2.

Indications

• Metastatic or unresectable colorectal adenocarcinoma, first-line. Also in BC Cancer's eligibility: appendiceal and small-bowel adenocarcinoma (GIFOLFIRI/GIFFIRB).
• Second-line after oxaliplatin-based therapy.
• After immunotherapy in MMR-deficient disease.
• BC Cancer specifies GIFFIRPAN for RAS wild-type disease when the patient is not suitable for bevacizumab, or has a left-sided tumour with no prior treatment in the advanced setting, regardless of bevacizumab eligibility.
• FOLFIRI is not an adjuvant regimen for colon cancer. Irinotecan added nothing in the adjuvant trials.

Regimen

FOLFIRI backbone. Source: BC Cancer GIFOLFIRI

Cycle length: 14 days. Duration: until progression or unacceptable toxicity. For FOLFIRI alone, BC Cancer adds "discontinue if no response after 2 cycles".

Biologic add-ons

Source differences to know

• Cetuximab. eviQ ID 1682 gives cetuximab 500 mg/m² every 2 weeks, and describes the two-weekly schedule as equally efficacious and more convenient than weekly. CRYSTAL used the original weekly schedule (400 mg/m² loading, then 250 mg/m² weekly).
• Leucovorin in eviQ 1682. eviQ uses leucovorin 50 mg flat IV bolus, not 400 mg/m².
• Bevacizumab dose. BC Cancer recalculates it if body weight changes by more than 10%.

Premedication and supportive care

• Antiemetics. Moderately emetogenic (BC Cancer SCNAUSEA; eviQ "MODERATE"). BC Cancer advises avoiding prochlorperazine on irinotecan days because of increased akathisia.
• Atropine. Atropine 0.3 mg SC treats early cholinergic symptoms: diarrhea or cramps within 24 h, rhinorrhea, salivation, lacrimation, diaphoresis and flushing. It may be repeated every 30 min to a maximum of 1.2 mg. Give it prophylactically in later cycles if these symptoms occurred (BC Cancer).
• Loperamide for late diarrhea (BC Cancer regimen). The patient must have a supply at home and start at the first loose stool:
• 4 mg stat;
• then 2 mg every 2 hours until diarrhea-free for 12 hours;
• 4 mg every 4 hours overnight is allowed.
• This is higher than the manufacturer's label.
• Add an oral fluoroquinolone if diarrhea persists despite loperamide, or if fever develops with diarrhea even without neutropenia. Admit for IV fluids if it lasts more than 48 h.
• Cetuximab premedication. eviQ lists an antihistamine (loratadine 10 mg PO) and dexamethasone 8 mg PO 60 min before. First-dose infusion reactions are the concern.
• Panitumumab skin pre-emption (BC Cancer). From cycle 1, for the first six weeks: doxycycline or minocycline 100 mg PO BID, plus clindamycin 2%/hydrocortisone 1% lotion. Also sunscreen, a hat, alcohol-free emollients, and no acne products. In STEPP, pre-emptive treatment halved grade ≥ 2 skin toxicity.
• Growth factor. Not routine. Consider after febrile neutropenia, or with prior pelvic radiotherapy, per local policy.

Key toxicities

Irinotecan

• Diarrhea. There are two syndromes.
• Early diarrhea is cholinergic, within 24 h, and responds to atropine.
• Late diarrhea starts at 5–11 days, lasts 3–7 days, and can be life-threatening with neutropenia.
• Neutropenia.
• Gilbert's syndrome / UGT1A1 poor metabolizers (e.g. UGT1A1*28 homozygous) are at higher risk. BC Cancer recommends screening for Gilbert's with direct/indirect bilirubin, and suggests preferring oxaliplatin-based therapy in these patients. Formal UGT1A1 genotyping practice varies by jurisdiction.
• Hepatic dysfunction. BC Cancer notes irinotecan has not been studied with bilirubin > 35 micromol/L. The risk of severe neutropenia rises at bilirubin 17–35 micromol/L.
• Alopecia, and rare pulmonary toxicity.

Fluorouracil (as for FOLFOX)

• Mucositis and diarrhea.
• DPD deficiency. BC Cancer requires baseline DPYD genotyping and doses by activity score. Guidance varies by country.
• Coronary vasospasm.
• Warfarin interaction.

Bevacizumab (BC Cancer GIFFIRB precautions)

• Hypertension. Common. Treat to target with calcium channel blockers, ACE inhibitors or diuretics. Discontinue for hypertensive crisis or hypertension that cannot be controlled.
• Proteinuria. Can progress to nephrotic syndrome.
• Bleeding. Stop bevacizumab for grade 3–4 hemorrhage. Stop NSAIDs and ASA > 325 mg/day.
• Arterial thromboembolism. Higher risk with prior arterial events or age > 65.
• Venous thrombosis. Hold 2 weeks for a grade 3 event.
• GI perforation and wound dehiscence. Can be fatal. Watch for abdominal pain with constipation or vomiting.
• Surgery. BC Cancer excludes patients within 28 days of major surgery.
• PRES/RPLS. Headache, seizures, visual change.

Anti-EGFR antibodies (panitumumab, cetuximab)

• Papulopustular (acneiform) rash. Typically starts in week 1–3 with a median around day 14, and crusts by week 4. Rash severity correlates with benefit, but that is no reason to leave it untreated.
• Paronychia, fissures, xerosis and trichomegaly.
• Hypomagnesemia. Can be delayed beyond 6 weeks and cause arrhythmia with hypokalemia.
• Infusion reactions (cetuximab more than panitumumab).
• Rare interstitial lung disease.
• Diarrhea is additive with irinotecan.

Monitoring

• Every cycle:
• CBC and differential, creatinine, total bilirubin, ALT.
• Diarrhea and stomatitis grade.
• Baseline DPYD test.
• Bevacizumab:
• BP before and after the dose for the first 3 cycles, then before each dose.
• Urine dipstick or lab urinalysis for protein at baseline and before every even-numbered cycle. If the dipstick is 2+ or 3+, or lab protein is ≥ 1 g/L, give the dose and collect a 24-h urine. If the dipstick is 4+, hold bevacizumab and collect a 24-h urine.
• INR at least every cycle on warfarin; hold bevacizumab if INR > 3.0.
• Panitumumab: magnesium before each cycle, plus calcium and potassium as indicated. Examine the skin at each visit.

Dose-modification principles

BC Cancer GIFFIRB / GIFFIRPAN dose levels:

• Day-1 thresholds. Hold if ANC < 1.5 × 10⁹/L (a higher threshold than for FOLFOX) or platelets < 75 × 10⁹/L. Recheck weekly up to 2 times, then discontinue if not recovered. Grade 3 cytopenia → reduce irinotecan and fluorouracil one level. Grade 4, or grade 4 neutropenia with fever → reduce two levels.
• Diarrhea. Hold for grade ≥ 2 on day 1. Grade 3 → one level down for irinotecan, fluorouracil and panitumumab. Grade 4 → two levels down.
• Bevacizumab is not dose-reduced. It is held or stopped:
• 24-h urine protein ≤ 2 g → full dose; > 2–4 g → hold and recheck every 2 weeks; > 4 g → discontinue.
• BP > 160/100 → continue and start or adjust antihypertensives.
• Hypertensive crisis → discontinue.
• Panitumumab rash.
• Grades 1–2: continue, with topical and oral antibiotic therapy.
• Grade 3: withhold 2–4 weeks until grade ≤ 2, then resume at 100%, 80%, then 60% of the previous dose for the 1st, 2nd and 3rd occurrence.
• Grade 4: discontinue.
• Magnesium (panitumumab).
• 0.4 to < 0.5 mmol/L: continue, with oral Mg plus magnesium sulfate 5 g IV every 2 weeks.
• < 0.3 mmol/L: hold panitumumab and give IV magnesium twice weekly.

Always use your institution's own tables.

Key trials and evidence

• Hurwitz (NEJM 2004). Adding bevacizumab to IFL improved overall survival in first-line mCRC. This established anti-VEGF therapy in the disease.
• CRYSTAL (Van Cutsem, NEJM 2009). Cetuximab plus FOLFIRI improved progression-free survival. The benefit was confined to KRAS wild-type tumours, which started biomarker selection.
• FIRE-3 (Heinemann, Lancet Oncol 2014). FOLFIRI + cetuximab vs + bevacizumab in KRAS exon 2 wild-type disease: similar response rate and progression-free survival, but longer overall survival with cetuximab.
• CALGB/SWOG 80405 (Venook, JAMA 2017). No overall survival difference between cetuximab and bevacizumab added to FOLFOX or FOLFIRI overall.
• Arnold (Ann Oncol 2017). Pooled analysis showing that primary tumour side is prognostic and predictive. Anti-EGFR benefit is concentrated in left-sided RAS wild-type tumours.
• PARADIGM (Watanabe, JAMA 2023). Prospectively showed longer overall survival with panitumumab than bevacizumab (plus mFOLFOX6) in left-sided RAS wild-type mCRC.

Clinical pearls

• Sidedness is anatomical. "Left-sided" means splenic flexure to rectum (BC Cancer's definition). Record it in the chart at the first consult.
• Never give an anti-EGFR antibody without extended RAS results. It can harm RAS-mutant patients, especially in combination with oxaliplatin.
• Diarrhea plans save lives. Confirm that the patient has loperamide at home and knows the 4 mg-then-2 mg-every-2-hours schedule. Tell them to call if diarrhea is not settling within 24 h, or if they develop fever.
• Plan surgery around bevacizumab. It impairs wound healing. Coordinate with the surgeon before elective procedures and port insertion. BC Cancer excludes patients within 28 days of major surgery.
• Start skin care on day 1 of an anti-EGFR antibody. Pre-emptive doxycycline or minocycline plus topical steroid/antibiotic reduces dose interruptions, and interruptions cost efficacy.
• Check magnesium even without symptoms. Hypomagnesemia can be severe and delayed. Oral magnesium often causes diarrhea, which is a problem on irinotecan, so IV repletion may be needed.
• Cetuximab and alpha-gal. Severe first-dose anaphylaxis to cetuximab is linked to pre-existing IgE against galactose-α-1,3-galactose, which is more common in some regions (e.g. after tick bites). Ask about red-meat allergy.

Educational material for health professionals and students. Not a prescribing order; it does not replace your institution's approved protocol, pharmacy verification or clinical judgement.

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