Growth factor injections: filgrastim and pegfilgrastim | CION Cancer Clinics

Both injections push your bone marrow to make white cells called neutrophils faster after chemotherapy. They shorten the days your count stays low, and that lowers the chance of a serious infection.

Why your count drops in the first place

Chemotherapy for leukaemia, lymphoma and myeloma is aimed at cells that divide quickly. The bone marrow, where blood cells are made, also divides quickly, so it is hit too. A few days after treatment the neutrophil count falls. Neutrophils are the cells that fight bacteria first, so while the count is low, an ordinary germ can turn into a serious infection within hours.

What the injection changes

Your body already makes a natural signal called G-CSF, which tells the marrow to make more neutrophils. Filgrastim and pegfilgrastim are manufactured copies of that signal. A larger amount of it makes the marrow work harder and release neutrophils sooner. The count still dips, but it usually climbs back up earlier than it would on its own.

What it does not do

It does not treat the blood cancer itself. It does not raise your platelets or your haemoglobin, and it does not stop an infection that has already started. It buys safer days between cycles, so that treatment can stay on schedule.

The most common effect is bone pain. It is usually a dull ache in the lower back, hips, thighs or breastbone. For most people it is mild and settles within a few days.

Other effects people notice

Some redness or soreness where the needle went in. A headache. Feeling tired or achy, a bit like the start of flu. A mild rise in temperature can happen too, which is exactly why you must never assume a fever is "just the injection". Treat every fever on low counts as an infection until a doctor says otherwise.

Managing the ache

Ask your team which pain relief is safe for you before you need it. Some common painkillers affect platelets or the kidneys, and some hide a fever. Do not pick one from the chemist on your own, and do not take anything to bring a temperature down before you have told the team about it.

Not everyone on chemotherapy needs a growth factor injection. When the chance of a very low count is small, the injection adds bone pain, cost and needles without much benefit. Your team weighs this for each treatment plan.

When the team may hold back or take extra care

People with a known allergy to these medicines should not have them. Extra caution is needed in sickle cell disease, where the injection can trigger a crisis, and in some myeloid leukaemias and marrow disorders, where the team must be sure it will not feed the disease. Tell your team about any past reaction, lung problem or spleen problem.

What this page cannot tell you

It cannot tell you whether you need the injection, which one, how much or for how long. It cannot tell you what your own count will do. Those depend on your diagnosis, your chemotherapy and your blood tests, and only your treating team has all three.