16.3 Colony-Stimulating Factors

TCO IV.C.3 tests colony-stimulating factors (CSFs) as supportive care, not as leukemia disease-modifying therapy. A 6-year-old finishing a solid-tumor cycle who needs filgrastim at home, a 45-kg adolescent due for pegfilgrastim the day after doxorubicin, and a toddler on a high-risk neuroblastoma antibody block that includes sargramostim are the pictures. ONCC uses generic names. Do not treat a brand injector color as exam fact.

The three agents and what they do

Filgrastim is granulocyte colony-stimulating factor (G-CSF). It is usually given subcutaneously once daily until the protocol’s absolute neutrophil count (ANC) recovery rule is met (some pathways use a defined ANC threshold or a set number of doses). It shortens severe neutropenia after myelosuppressive chemotherapy and is used after selected autologous transplants as protocol-directed marrow recovery support. Teach families a real injection: rotate sites, do not shake the vial, and do not skip doses because the child “looks fine today.”

Pegfilgrastim is pegylated long-acting G-CSF, typically one dose per chemotherapy cycle. Adult and larger-child labeling commonly uses 6 mg once for patients at or above a protocol weight tier (often 45 kg); smaller children receive weight-based or syringe-device doses printed on the protocol. Pegfilgrastim is not for every infant weight. A 6-kg infant is not automatically given an adult 6 mg prefilled syringe because “that is what the cabinet had.” Follow the protocol’s milligram amount and whether that cycle even uses pegfilgrastim versus daily filgrastim.

Sargramostim is granulocyte-macrophage colony-stimulating factor (GM-CSF). It stimulates neutrophils and monocytes/macrophages. Pediatric oncology nurses see it most clearly in some neuroblastoma antibody regimens (dinutuximab-era cooperative-group backbones that pair anti-GD2 antibody with GM-CSF). It is not interchangeable with filgrastim on an ALL maintenance calendar. If the protocol names sargramostim, do not substitute G-CSF because the pharmacy is short without the team rewriting the orders.

Timing: not the same afternoon as cytotoxic chemo

CSFs are not typically given the same day as cytotoxic chemotherapy. Many pediatric protocols round to about 24 hours after the last myelosuppressive dose. Pegfilgrastim labeling keeps the drug out of the window from 14 days before through 24 hours after cytotoxic chemotherapy because concurrent CSF can theoretically increase marrow sensitivity to chemo or blunt the intended recovery schedule. Same-day pegfilgrastim “while we already have a needle in” is the classic clinic shortcut the exam will punish. If a protocol explicitly uses a same-day device or a timed on-body injector, that is a protocol exception—teach the exception as written, not as a new national default.

A 9-year-old who finishes ifosfamide at 16:00 does not get pegfilgrastim at 16:10. Schedule it the next calendar day in the 24-hour neighborhood the protocol names. Daily filgrastim follows the same logic: start when the protocol says after chemo, not during the infusion.

Bone pain, rare splenic rupture, and ANC monitoring

Bone pain—pelvis, sternum, long bones—is the expected adverse effect as marrow wakes up. It can be intense in adolescents. Treat with protocol-allowed analgesics (acetaminophen; nonsteroidal anti-inflammatory drugs only if platelets, renal function, and high-dose methotrexate windows allow). Some programs add an antihistamine for pegfilgrastim-associated bone pain per order; it is not an ONCC-mandated home recipe from a parent’s purse. Do not withhold CSF solely because of predictable ache without talking to the team; do not ignore pain that is localized, sudden, and accompanied by shock.

Splenic rupture is rare. Left-upper-quadrant pain, left shoulder-tip pain, abdominal distention, or hypotension after recent CSF is an emergency workup for splenic capsular injury, not “growing pains from the shot.” Hold further doses and get the child to a monitored setting. Teach families this one sentence at discharge so they do not wait until morning clinic.

ANC monitoring is how you know the drug worked and how you know it overshot. Recheck counts on the protocol calendar. Call for unexpected leukocytosis, new hypoxia, or the rare leukostasis picture. Filgrastim is usually stopped when the protocol ANC stop-rule is met; extra “just in case” doses after recovery are not a nursing improvisation.

AML, neuroblastoma antibody, and infant traps

Do not use CSF in acute myeloid leukemia without protocol direction. Historical and biologic concern is that G-CSF or GM-CSF can stimulate leukemic blasts. Some AML trials use CSF at defined times (for example, after induction nadir once blasts are cleared, or for life-threatening infection); that is a written protocol, not a clinic reflex because the ANC is 40/µL on day 8 of induction. A 3-year-old with new AML and circulating blasts who is handed a filgrastim syringe “like the solid-tumor kids” is the wrong map.

GM-CSF in some neuroblastoma antibody regimens is the other pediatric exception to remember. Dinutuximab (anti-GD2) pathways have used sargramostim as an immune adjunct, not merely as a neutropenia shortcut. Pain, capillary leak, and hypotension on those days are antibody toxicities owned in the immunotherapy chapter; this section’s job is to keep GM-CSF on the calendar when the protocol put it there and not to drop it because the ANC already recovered.

Infant weight is the third trap. Pegfilgrastim autoinjectors sized for adolescents are not infant devices. If the protocol uses daily filgrastim in a 7-kg child, that is the plan. If it uses a tiny pegfilgrastim dose from a vial, draw what is ordered. Do not round a 6 mg adult syringe down by eyeball.

The CPHON product is a CSF given about a day after cytotoxic chemo, a family warned about bone pain and rare splenic pain, a pegfilgrastim dose that matches weight and protocol, GM-CSF still present on a neuroblastoma antibody roadmap, and no freelance filgrastim on an AML induction without a protocol line that says so.