Mobilization for PBSC

Overview

Before apheresis collection, you mobilize stem cells into your bloodstream. You inject yourself with filgrastim daily for 4-5 days. This growth factor signals your bone marrow to push stem cells out into your blood where they can be collected.

Real side effects happen during mobilization. The most common is bone pain, which many donors feel in their bones, ribs, or pelvis. Pain peaks around day 4 or 5 and usually responds well to over-the-counter medicine. Tiredness and mild headaches are also common. All side effects stop when you finish the injections, usually within days of your last dose.

How does mobilization work?

Mobilization is the process of moving stem cells from your bone marrow into your peripheral blood, where they can be collected. It's the first step for PBSC donors and involves daily injections of filgrastim (also called G-CSF) for 4-6 days.

Mobilization overview. The process involves:

• Daily filgrastim injections for 4-6 days
• Increases white blood cell production in marrow
• Mobilizes stem cells into peripheral blood
• Blood tests monitor readiness (usually day 4-5)
• Collection starts when cells reach target level
• Usually takes 4-5 days total

What is mobilization?

Your bone marrow produces all your blood cells, including stem cells needed for transplant. Normally, stem cells stay in the marrow. Filgrastim is a growth factor that increases white blood cell production and mobilizes stem cells into the blood. By injecting filgrastim daily, you create high concentrations of stem cells in your bloodstream where they can be collected.

The goal is getting enough stem cells for the recipient to receive an effective dose. The transplant team determines how many cells are needed (typically 2-5 million CD34+ cells per kilogram of recipient body weight). You'll be collected multiple times if needed until this goal is reached.

Filgrastim injections

How to give the injections

Your coordination center will teach you how to inject filgrastim, or bring someone to learn. The injection is subcutaneous—a short needle goes just under the skin, usually on the belly, thigh, or arm. Each injection is quick (2-3 seconds) and uses a tiny needle.

Injection technique. The proper steps:

• Pinch skin slightly at injection site
• Insert needle at 45-90 degree angle
• Inject medication slowly
• Withdraw needle
• Most people feel minimal pain (just a pinch)
• Rotate injection sites to prevent trauma

Your center provides pre-filled syringes or pens. Before each injection, verify the medication (label, dose, expiration date). Use a new needle each time. Document the injection (date, time, location) so your team can track your response. Rotating locations prevents repeated trauma to one spot.

Side effects

Common side effects. Most donors experience:

• Bone pain (70-90% of donors)—most common
• Fatigue and exhaustion (highly variable)
• Headache
• Mild muscle aches
• Rarely: fever as marrow ramps up
• Pain peaks around day 4-5 of injections
• All side effects resolve after stopping medication

Bone pain typically starts on day 2-3 of injections and peaks around day 4-5. It's usually described as a dull ache in the bones, ribs, pelvis, or joints—sometimes severe enough to wake you at night, sometimes mild. Other side effects like fatigue and headache are usually mild and resolve quickly.

Most side effects are managed with over-the-counter pain medication. Ibuprofen or naproxen are most effective because they reduce inflammation. Taking medication every 6-8 hours regularly (not just when pain strikes) works better than waiting for pain to peak then treating it.

How long does mobilization take?

Typical timeline. Your mobilization follows this pattern:

• Typically 4-5 days total (can be 4-6 days)
• Inject on days 1-4 or 1-5 depending on response
• Blood test on day 4 or 5 morning to assess CD34+ count
• Collection starts when CD34+ count is adequate

The adequate target is usually a CD34+ count of 20 cells per microliter or higher. Your medical team monitors your response through blood tests and adjusts your timeline accordingly.

Individual variation. Mobilization timing depends on several factors:

• Your bone marrow's responsiveness to filgrastim
• Previous chemotherapy history
• Current medications you're taking
• Underlying health conditions
• Age and overall fitness level
• Your baseline CD34+ count level

Your medical team evaluates all these factors when estimating your timeline. Previous chemotherapy or certain medications can slow mobilization somewhat, but most donors still respond well to the growth factor.

Some donors mobilize quickly and are ready on day 4. Others need the full 5-6 days. Neither is better or worse—it reflects individual variation in how your bone marrow responds to the growth factor. Previous chemotherapy, certain medications, or certain diseases can slow mobilization somewhat.

Rarely, mobilization is inadequate despite full treatment. This occurs in less than 3% of donors and doesn't mean anything is wrong with you. Your team will discuss options if this happens—you might continue injections longer, collect anyway with extra collection days, or rarely switch to bone marrow collection as an alternative.

Managing side effects

Medication approaches. Effective pain control strategies include:

• Start medication on day 2 (before pain peaks)
• Consistent dosing works better than as-needed dosing
• Ibuprofen or naproxen most effective for inflammation
• Acetaminophen less effective but can combine with NSAIDs
• Prescription opioids available if over-the-counter insufficient

Talk with your team before mobilization starts about all pain management options. Some donors need stronger medication; others do well with over-the-counter options.

Non-medication strategies. Other approaches that help significantly:

• Heat pads for 15-20 minutes on achy areas
• Warm baths or showers relax muscles and ease pain
• Gentle exercise like walking maintains fitness without stressing joints
• Stay well-hydrated (Filgrastim can cause mild dehydration which worsens pain)
• Drink 2-3 liters of water daily

Limit caffeine and alcohol during mobilization, as both can worsen dehydration and increase pain. Many donors find that combining several strategies—medication, heat, hydration, and gentle movement—works best for managing bone pain during this period.

When to contact your team

Most mobilization side effects are expected and manageable. However, some symptoms warrant immediate evaluation. Your medical team is available to assess any concerning symptoms during this important preparation phase.

Warning signs. Contact your center immediately if you develop:

• Fever, especially above 101.5F (could indicate serious infection)
• Severe bone pain that doesn't respond to medication
• Unusual bleeding or bruising (unexpected or progressive)
• Severe shortness of breath or chest tightness

Additional concerns. Also call for:

• Severe abdominal pain (could indicate splenic rupture, though very rare)
• Redness, warmth, or swelling at injection sites
• Persistent severe headache that doesn't improve

Most symptoms during mobilization are expected side effects. But your medical team wants to evaluate anything that concerns you. When in doubt, contact them—it's better to ask about a symptom that ends up being normal than to miss something important. Your team has evaluated hundreds of mobilizing donors and can quickly assess whether your symptoms need attention or are routine.