G-CSF (Granulocyte Colony-Stimulating Factor)

G-CSF (granulocyte colony-stimulating factor) is a drug treatment that helps your body make white blood cells called neutrophils. Neutrophils are your body’s most common type of white blood cell. They help fight germs that cause infections. Low neutrophil levels (neutropenia) can make it harder to fight infections. Severe neutropenia can be life-threatening.

Healthcare providers use G-CSF to treat and prevent severe neutropenia. It works in your bone marrow, where blood cells are made. G-CSF tells an early blood cell (stem cell) to become a neutrophil. It also helps neutrophils to multiply so you have more of them to fight infections.

You may receive G-CSF:

• After chemotherapy: Chemotherapy drugs kill cancer cells. But they can also harm healthy cells, like neutrophils. G-CSF helps your bone marrow make more neutrophils so that you don’t get a serious infection.
• Before and after a stem cell transplant: G-CSF helps your body make healthy stem cells. Your provider may collect the stem cells before you get high-dose chemotherapy to kill abnormal blood cells. They’ll give the stem cells back to you to replace the abnormal cells. You may also need G-CSF afterward to help neutrophils recover and prevent infection.
• As needed, for chronic neutropenia: Some people are born with lifelong neutropenia. When this happens, you may need G-CSF injections at certain times in your life when low neutrophil levels put you at risk of a serious infection.

What are the different types of G-CSF?

G-CSF is also known as filgrastim (Neupogen^®). Several forms of filgrastim are available under different brand names. These medications, called biosimilars, aren’t identical to filgrastim but are just as safe and effective. They include:

• Filgrastim-aafi (Nivestym^®)
• Filgrastim-sndz (Zarxio^®)
• Filgrastim-ayow (Releuko^®)

Lenograstim (Granocyte™, Neutrogin™, Myelostim™) is another G-CSF with uses like filgrastim.

Pegfilgrastim (Neulasta^®) is a long-acting form of filgrastim. Because it stays in your body longer, you don’t need injections as often.

What happens during this treatment?

First, your cancer doctor (oncologist) or blood specialist (hematologist) will do blood tests to check your neutrophil levels. They’ll also consider your risk of developing a serious infection. Not everyone with neutropenia needs G-CSF.

G-CSF is usually given as a shot just under your skin, often in a fatty area like your upper arm, belly or thigh. You’ll likely feel a quick sting or pressure when the needle goes in. You may get injections at a clinic, or your provider may teach you how to give the shots to yourself at home.

Sometimes, providers give G-CSF through a vein (IV infusion). You’ll receive this treatment in a hospital or infusion center.

When is G-CSF given?

G-CSF usually starts a day or two after chemotherapy ends. Healthcare providers often give it four to six days before they collect stem cells for a transplant. You’ll likely receive daily injections unless you take the long-lasting form, pegfilgrastim. You may only need one shot between chemotherapy treatments if you take pegfilgrastim.

For chronic neutropenia, you may only need a single injection when your neutrophil counts are so low that you’re at serious risk of an infection.

Your healthcare provider will explain your treatment timeline.

What is the most common side effect of G-CSF?

The most common side effect is bone pain that may feel like a deep ache. It usually starts one to three days after your first dose. The pain goes away once you stop taking G-CSF.

Many people describe the pain as mild to moderate. Talk to your healthcare provider if it’s difficult to manage. They may recommend NSAIDs or antihistamines (like loratadine) to help relieve it.

How long does it take for G-CSF to work?

It usually takes about a week for your bone marrow to make new cells with G-CSF. Most people taking G-CSF after chemotherapy continue treatment until their blood counts return to normal.

Is there anything I can do to make this treatment easier on me?

Try to rest as much as you can after a G-CSF injection. Remember that your bone marrow is working hard to make more blood cells. Allow your body to put your energy toward making the neutrophils you need to stay well.

When should I call my healthcare provider?

Tell your healthcare provider about any side effects you have while taking G-CSF. Before starting treatment, ask which side effects require emergency medical attention.

Warning signs include:

• Signs of an infection, like a fever, chills or a sore throat
• Signs of an allergic reaction, like a rash, swelling or trouble breathing
• Shortness of breath
• Rapid heartbeat
• Sudden swelling in your arms or legs

Is G-CSF the same as filgrastim?

Yes. Filgrastim is the most common form of G-CSF in the United States.