FOLFIRI

Say it: foll-FEER-ee

Leucovorin, fluorouracil and irinotecan

FOLFIRI is a three medicine chemotherapy plan used mostly for colon and rectal cancer that has spread.

Also called: FOLFIRI plus bevacizumab, FOLFIRI with cetuximab, FOLFIRI with panitumumab, Modified FOLFIRI, FOLFIRI-bevacizumab, 5-FU, leucovorin and irinotecan

What it is

Fluorouracil (5-FU) and irinotecan attack cancer cells in two different ways, and leucovorin helps fluorouracil work better. It is often used as a first treatment for cancer that has spread, or as the next step after FOLFOX. The goal is to shrink or control the cancer, help you live longer and keep you feeling as well as possible.

Often used for

• Colon or rectal cancer that has spread
• Colon or rectal cancer that grew after FOLFOX
• Some stomach and esophagus cancers

FOLFIRI plus bevacizumab

A common plan for cancer that has spread, including after FOLFOX stops working. Bevacizumab helps block the tumor's blood supply and can raise blood pressure.

FOLFIRI plus cetuximab

Only for tumors with normal RAS genes (RAS wild type, and usually BRAF normal too), most often tumors that started on the left side of the colon or in the rectum. It often causes an acne-like rash.

FOLFIRI plus panitumumab

Same idea as cetuximab: only for RAS wild type tumors, usually left sided. It commonly causes an acne-like rash, dry skin and low magnesium.

The medicines in this plan

Leucovorin

A form of folic acid that makes fluorouracil work better. Given through a vein over about 2 hours on day 1.

Fluorouracil (5-FU)

Chemotherapy that stops cancer cells from copying their DNA. A quick push on day 1, then a small take-home pump gives the rest over about 46 hours.

Irinotecan

Chemotherapy that breaks cancer cell DNA. Given through a vein over about 90 minutes on day 1. It is the main cause of diarrhea with this plan.

Bevacizumab

Only in the bevacizumab version. An antibody that cuts off the blood vessels tumors need. Given through a vein on day 1.

Cetuximab

Only in the cetuximab version. An antibody that blocks a growth signal (EGFR) on cancer cells. Given through a vein every 1 or 2 weeks.

Panitumumab

Only in the panitumumab version. An antibody that blocks the same growth signal (EGFR). Given through a vein on day 1.

How you get it

FOLFIRI is given in an outpatient infusion clinic, usually through a port (a small device under the skin of the chest). Day 1 in the clinic takes about 3 to 5 hours, then a small pump at home finishes the fluorouracil over about 2 days. Each cycle is 14 days, and it usually continues as long as it is working and you are handling it well. Your schedule may be different.

A typical cycle

Day 1

Blood tests and a check in. Anti-nausea medicines, then irinotecan and leucovorin through your port, plus any antibody add-on. A quick push of fluorouracil, then the take-home pump is connected.

Days 1 to 3

The pump gives fluorouracil at home for about 46 hours. Watch for diarrhea starting.

Day 3

The pump is disconnected at the clinic or by a home nurse.

Days 4 to 14

Rest and recovery. Late diarrhea can show up during this time. Blood counts are often lowest around days 7 to 12.

Common side effects and what helps

• Diarrhea, which can start days after treatment. Start your diarrhea medicine at the first loose stool, as your team taught you, and drink lots of fluids.
• Cramping, sweating, watery eyes or runny nose during or soon after irinotecan. Tell the nurse right away; a quick medicine can stop it.
• Nausea and vomiting. Take anti-nausea medicines on schedule.
• Tiredness. Rest when you need to and keep up light activity.
• Hair thinning or hair loss. A soft hat or scarf can help.
• Low blood counts and higher infection risk. Wash hands often and avoid crowds and sick people.
• Mouth sores. Rinse often with a mild salt and baking soda rinse.
• With cetuximab or panitumumab: an acne-like rash on the face, chest and back. Use gentle soap, thick moisturizer and sunscreen, and ask about rash medicines.

Call your care team right away if you have

• A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills
• Diarrhea that does not get better within 24 hours of starting your diarrhea medicine, or 4 or more extra stools a day
• Diarrhea together with fever, or feeling dizzy or faint
• Vomiting that keeps you from drinking or taking medicines
• Chest pain or trouble breathing
• Bleeding that will not stop, or black stools
• A problem with your pump, such as a leak, alarm or wet bandage
• Severe belly pain

Good to know

• Diarrhea with fever can be dangerous because you can lose fluid and get an infection at the same time. Call right away.
• Some people have gene changes (UGT1A1 and DPD) that make irinotecan or fluorouracil much stronger. Ask whether testing is right for you.
• You will have blood tests before each cycle.
• Cetuximab and panitumumab only help when tumor testing shows normal RAS genes, so this testing is done first.
• Bevacizumab is usually paused for several weeks around surgery because it slows wound healing.

At home

• Keep your diarrhea medicine at home before your first cycle, and follow the exact plan your team gave you.
• Drink about 8 to 10 cups of fluid a day, more if you have diarrhea. Drinks with salt and sugar (like oral rehydration drinks) help.
• Keep the pump in its carry case and keep it dry. Never pull on the tubing.
• Eat small, bland meals on bad days and avoid greasy or spicy food.
• Use sunscreen and a hat, especially with cetuximab or panitumumab.

Questions to ask

• What is the goal of my treatment, and how will we know it is working?
• Will an antibody be added, and why that one?
• What were my tumor's RAS and BRAF results?
• Exactly how should I take my diarrhea medicine, and when should I call?
• Should I have UGT1A1 or DPD gene testing?

Colorectal cancer

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.