Growth Factors

Overview, hematopoietic growth factors used in oncology

• Myeloid (G-CSF / GM-CSF): filgrastim, pegfilgrastim, biosimilars, eflapegrastim, efbemalenograstim alfa, lipegfilgrastim, tbo-filgrastim; sargramostim (GM-CSF).
• Erythroid (ESAs): epoetin alfa, darbepoetin alfa, biosimilar epoetin.
• Thrombopoietin receptor agonists (TPO-RAs): romiplostim, eltrombopag, avatrombopag, lusutrombopag.
• Board-prep frame: know indication thresholds (FN ≥20% for G-CSF, Hb <10 for ESA), black-box risks (ESA tumor/VTE), and scenarios to AVOID growth factors (concurrent chemoradiation, curative-intent ESA, sickle cell on G-CSF).

Myeloid growth factors (G-CSFs)

Mechanism

• G-CSF (filgrastim, pegfilgrastim): binds the G-CSF receptor on neutrophil precursors, driving proliferation, differentiation, and accelerated release from marrow. Shortens the duration and depth of neutropenia.
• GM-CSF (sargramostim): broader stimulation of granulocytes, macrophages, eosinophils; more constitutional side effects, narrower indications.

Agents and dosing

• Filgrastim: short-acting, 5 µg/kg SC daily, starting 24 to 72 h after chemo, continued until ANC recovery (typically 7 to 14 days).
• Pegfilgrastim: pegylated, T½ ~33 h, single 6 mg SC dose per chemo cycle 24 h after chemo. Cleared by a neutrophil-mediated mechanism (self-regulating clearance).
• Eflapegrastim (Rolvedon, approved 2022): novel long-acting G-CSF with an Fc fragment; non-inferior to pegfilgrastim for duration of severe neutropenia with docetaxel/cyclophosphamide (TC).
• Efbemalenograstim alfa (Ryzneuta, approved 2023): long-acting Fc-fusion G-CSF.
• Biosimilars: filgrastim-sndz/aafi/ayow, pegfilgrastim-jmdb/cbqv/bmez/apgf/pbbk, therapeutically equivalent (none FDA-designated interchangeable).
• Sargramostim (GM-CSF): 250 µg/m²/day SC; primarily after autologous SCT for engraftment and some refractory FN settings (adjuvant GM-CSF in melanoma, E4697, did not improve RFS or OS).

Indications

• Primary prophylaxis (give with cycle 1): regimens with FN risk ≥20%; or 10 to 20% with high-risk patient features (age >65, advanced disease, prior chemo/RT, ECOG ≥2, marrow involvement, prior FN, open wounds, hepatic/renal dysfunction, HIV).
  • High-FN-risk regimens (representative): TAC (breast), AC→T dose-dense (breast), TC (docetaxel/cyclophosphamide), R-CHOP-14, hyperCVAD, BEACOPP-escalated, ICE, DA-EPOCH-R for Burkitt, topotecan, TIP (paclitaxel, ifosfamide, cisplatin).
• Secondary prophylaxis: any patient with prior FN or dose-limiting neutropenia on a prior cycle, where reduced dose intensity would compromise outcomes (curative or potentially curative settings).
• Therapeutic use for established febrile neutropenia: not routine; consider in high-risk patients (ANC <100 expected >10 d, age >65, uncontrolled disease, pneumonia, hypotension, sepsis syndrome, invasive fungal infection, hospitalization at fever onset).
• Stem cell mobilization: filgrastim 10 µg/kg/day SC, alone or with plerixafor (CXCR4 inhibitor); pegfilgrastim also active. Goal CD34+ ≥2 × 10&sup6;/kg per transplant.
• Post-autologous or allogeneic SCT: shortens the duration of neutropenia (does not improve survival).
• Acute radiation syndrome (hematopoietic subsyndrome): FDA-approved for filgrastim, pegfilgrastim, and sargramostim.
• Congenital / chronic / cyclic neutropenia: long-term filgrastim (Dale 1993, Blood; PMID 8490166).
• Routine use NOT recommended: most AML induction (controversial; may use post-induction in older adults to shorten neutropenia, but no OS benefit), MDS (except low-risk symptomatic neutropenia, often combined with an ESA).

Dose-dense and interval-compressed regimens requiring growth-factor support (source notes)

• Dose-dense AC→T and other q2-week regimens require G-CSF support (daily filgrastim or a long-acting G-CSF such as pegfilgrastim) to enable cycle compression; CALGB 9741 used filgrastim; neutrophil recovery cannot keep pace without it.
• ddMVAC with G-CSF ×3 to 6 cycles is a standard-of-care neoadjuvant regimen for muscle-invasive bladder cancer (cT2 to cT4a, N0-1, M0), improving pathologic complete response.
• Interval-compressed VDC/IE q2wk with growth-factor support (AEWS0031) improves EFS and, on long-term follow-up, OS versus q3wk across localized Ewing sarcoma (AEWS0031 enrolled patients under 50 y); benefit is not restricted by an age-18 cutoff.

Adverse events, high-yield

• Bone pain (~25 to 40%): low back, sternum, pelvis; loratadine 10 mg daily may lessen severity (NOLAN phase 2, primary endpoint not met; Kirshner JJ et al, Support Care Cancer 2018; PMID 29147854). NSAIDs/acetaminophen also helpful.
• Splenic rupture: rare, reported in donors and sickle cell patients; usually preceded by LUQ pain.
• Sickle cell crisis / vaso-occlusive event: avoid G-CSF in sickle cell disease unless there is a transplant indication and a careful risk discussion.
• Pulmonary toxicity / ARDS: rare, particularly with GM-CSF (capillary leak).
• MDS / AML risk: a small absolute increase when G-CSF is added to chemotherapy (absolute increase ~0.4%, with lower all-cause mortality; Lyman GH et al, JCO 2010; PMID 20385991). The benefit in FN reduction generally outweighs this risk.
• Allergic / anaphylactic reactions: uncommon; cross-reactivity between filgrastim and pegfilgrastim is possible.
• Do not administer within 24 h before or after cytotoxic chemotherapy (pegfilgrastim label: not between 14 days before and 24 h after chemotherapy) (proliferating myeloid precursors are more chemosensitive; theoretical risk of worsening cytopenias).
• Concurrent chemoradiation: avoid G-CSF with concurrent thoracic/mediastinal RT, increased pulmonary and thrombocytopenia risk (Bunn PA et al, JCO 1995, GM-CSF in LS-SCLC chemoradiation; PMID 7602352).

Pearls

• Pegfilgrastim is preferred over daily filgrastim when ≥10 days of coverage is needed (convenience, equivalent efficacy).
• For dose-dense AC→T (q2-week) regimens, G-CSF support (daily filgrastim, as in CALGB 9741, or pegfilgrastim) is required to enable cycle compression; without it, neutrophil recovery cannot keep pace.
• Same-day pegfilgrastim (within 24 h of chemo) should be given at least 24 h after chemotherapy; same-day dosing produces deeper and longer neutropenia even in 3-week regimens and is not label-concordant (the on-body injector instead delivers drug about 27 h later).

Erythropoiesis-stimulating agents (ESAs)

Mechanism and agents

• Epoetin alfa and darbepoetin alfa (longer T½ via hyperglycosylation) bind the erythropoietin receptor, increasing RBC precursor proliferation and maturation.
• Effect on Hb takes 2 to 6 weeks; iron stores must be adequate (ferritin ≥100, TSAT ≥20%; supplement IV iron if functional deficiency).

Indications

• Chemotherapy-induced anemia in patients receiving palliative (non-curative) intent chemotherapy with Hb <10 g/dL who decline transfusion or for whom transfusion logistics are problematic.
• Lower-risk MDS with symptomatic anemia and EPO <500 mU/mL, high response rates (often combined with G-CSF for sideroblastic/MDS-RS).
• Hb target: the lowest level needed to avoid transfusion; do not exceed Hb 11 to 12 g/dL (FDA black-box).

Contraindications / avoid

• Curative-intent chemotherapy or chemoradiation: avoid ESAs (harm signals when Hb pushed high or used outside chemo-induced anemia). BEST studied metastatic (noncurative) breast cancer; ENHANCE studied head and neck cancer treated with radiotherapy.
• Active cancer not receiving chemotherapy.
• Uncontrolled hypertension, recent VTE or arterial thrombosis.

Adverse events

• Thromboembolism (VTE and ATE): ~50% relative increase; risk-stratify (Khorana score), avoid if recent VTE.
• Hypertension.
• Possible tumor progression / shortened survival when Hb is pushed >12 g/dL or used outside chemo-induced anemia (BEST in metastatic breast cancer, ENHANCE in head and neck cancer).
• Pure red cell aplasia (anti-EPO antibodies): rare, more historic.

Patient counseling (high-yield; ESA APPRISE REMS eliminated by FDA in 2017)

• Risk-benefit discussion documented; written informed consent in some institutions.
• Reassess every 4 weeks; discontinue if <1 g/dL Hb rise after 8 weeks (non-response); otherwise reduce or hold dose when Hb reaches the lowest level needed to avoid transfusion, then resume at a lower dose (not a permanent stop at Hb >11).
• Discontinue the ESA upon completion of the chemotherapy course.
• Assess iron status and correct iron deficiency; supplemental iron (preferably IV) may improve ESA response but is not mandatory in iron-replete patients.
• Reference: Bohlius J et al, ASCO/ASH 2019 update (JCO 2019; PMID 30969847).

Thrombopoietin receptor agonists (TPO-RAs) for chemotherapy-induced thrombocytopenia (CIT)

Agents

• Romiplostim: SC weekly, an Fc-peptibody acting on the same site as TPO. Increasing evidence for CIT, phase II RCT (Soff GA et al, JCO 2019; PMID 31545663) showed durable platelet recovery; phase III RECITE (NEJM 2026) positive in persistent CIT with GI cancers (not yet FDA-approved for CIT).
• Avatrombopag: oral, also FDA-approved for periprocedural use in chronic liver disease and ITP; phase 3 in solid-tumor CIT negative (Al-Samkari, Lancet Haematol 2022); randomized phase 2 ACT-GI positive in persistent CIT (JCO 2026).
• Eltrombopag: oral, used predominantly for ITP, aplastic anemia, and HCV-associated thrombocytopenia; off-label for CIT.
• Lusutrombopag: niche, periprocedural in chronic liver disease.

NCCN/clinical use in CIT

• Romiplostim now supported (NCCN 2024) for CIT with persistent grade 3 to 4 thrombocytopenia delaying subsequent chemotherapy, in solid tumors. Not routinely used in heme malignancies.
• Avoid in MDS / AML (concern for marrow fibrosis or blast progression; eltrombopag in MDS remains investigational outside specific trials).

Adverse events

• Headache, fatigue, arthralgia.
• Thrombosis: increased risk, particularly with eltrombopag.
• Marrow reticulin fibrosis (reversible) with long-term use.
• Hepatotoxicity: eltrombopag in particular.
• Reference: Soff GA et al, Cancer Med 2024 review (Cancer Med 2024; PMID 39135303).

Key historical and guideline references

• Filgrastim phase III (small-cell lung cancer): Crawford J et al, NEJM 1991; PMID 1711156, reduced FN incidence from 77% to 40% with filgrastim during CAE chemotherapy.
• Pegfilgrastim in breast cancer: Vogel CL et al, JCO 2005; PMID 15718314, pegfilgrastim vs placebo with docetaxel 100 mg/m² reduced FN from 17% to 1%.
• ASCO WBC growth factors guideline: Smith TJ et al, JCO 2015; PMID 26169616, risk threshold for primary prophylaxis ≥20%. Updated 2026 (JCO-25-02938) to incorporate eflapegrastim and efbemalenograstim.
• ASCO/ASH ESA guideline: Bohlius J et al, JCO 2019; PMID 30969847, non-curative chemo-induced anemia, Hb target <12.
• Severe chronic neutropenia: Dale DC et al, Blood 1993; PMID 8490166, long-term filgrastim is safe and effective.

2024-2026 growth-factor and cytopenia-support updates

• Luspatercept (Reblozyl): FDA Aug 2023 expanded to first-line ESA-naive lower-risk MDS with anemia (COMMANDS, Platzbecker Lancet 2023): transfusion independence plus Hb rise 1.5 g/dL for 12 wk achieved 58.5% (luspatercept) vs 31.2% (epoetin alfa). Displaces ESA as first-line for many lower-risk MDS.
• Imetelstat (Rytelo): FDA Jun 2024, telomerase inhibitor for lower-risk MDS with transfusion-dependent anemia (≥4 units RBC/8 wk) after ESA failure (IMerge, Zeidan Lancet 2024): 8-wk RBC-TI 40% vs 15% placebo; 24-wk TI 28% vs 3%. Cytopenias are the dominant AE.
• Momelotinib (Ojjaara): FDA Sep 2023 for intermediate/high-risk MF with anemia (MOMENTUM, Verstovsek Lancet 2023): JAK1/2 + ACVR1 inhibitor targets hepcidin-driven anemia; symptom-score TSS-50% ~25%, TI-response ~30% at wk 24. First FDA-approved MF therapy specifically for patients with anemia (MOMENTUM primary: TSS50; key secondary: transfusion independence).
• Romiplostim for CIT (RECITE phase 3): Al-Samkari NEJM 2026, persistent CIT on oxaliplatin-based GI chemotherapy; no CIT-related chemo dose modification 84% vs 36% placebo. Avatrombopag phase 3 (Lancet Haematol 2022) was negative in patients on chemotherapy without prior persistent CIT; phase 2 ACT-GI (JCO 2026) positive in persistent CIT. No TPO-RA is FDA-approved for CIT yet.
• Hetrombopag: novel oral TPO-RA, China approved (2021) for ITP; expanding to CIT/AA globally; not yet FDA-approved.
• Pegfilgrastim biosimilar landscape mature: pegfilgrastim-jmdb (Fulphila), -cbqv (Udenyca), -bmez (Ziextenzo), -apgf (Nyvepria), -pbbk (Fylnetra), -fpgk (Stimufend): biosimilars, not FDA-designated interchangeable. Prescriber-directed switching does not require an interchangeability designation. On-body injectors exist for some biosimilars under their own brand (e.g., Udenyca Onbody for pegfilgrastim-cbqv, FDA Dec 2023); these are not Neulasta Onpro.
• Efbemalenograstim alfa (Ryzneuta): FDA Nov 2023, Fc-fusion long-acting G-CSF; non-inferior to pegfilgrastim for duration of severe neutropenia (GC-627 phase 3).
• Eflapegrastim (Rolvedon): FDA Sep 2022, long-acting G-CSF with an Fc fragment; ADVANCE/RECOVER phase 3 non-inferior to pegfilgrastim.
• ASCO myeloid growth factor guideline update 2026 (JCO-25-02938): incorporates eflapegrastim and efbemalenograstim as equivalent options; reaffirms the ≥20% FN risk threshold; strengthens secondary prophylaxis when dose intensity matters.
• Elranatamab/teclistamab-related neutropenia plus G-CSF: prolonged neutropenia is common; growth-factor support is standard, especially in real-world cohorts.

Board-prep high-yield summary

• G-CSF primary prophylaxis if FN risk ≥20%, or 10 to 20% with risk factors.
• Pegfilgrastim = preferred long-acting agent; G-CSF (filgrastim or pegfilgrastim) required for dose-dense regimens.
• Avoid G-CSF in sickle cell disease, with concurrent thoracic chemoradiation, or within 24 h before or after cytotoxic chemo (pegfilgrastim: not from 14 days before to 24 h after).
• Bone pain: loratadine may help but benefit is uncertain (NOLAN negative primary endpoint); NSAIDs/acetaminophen also used.
• ESA for chemo-induced anemia only in non-curative chemo, Hb <10, target lowest Hb to avoid transfusion (do not exceed 11 to 12); separately, ESAs remain an option in lower-risk MDS with EPO <500, including patients not on chemo.
• ESA risks: VTE, tumor progression; counsel and document.
• Iron status must be checked with ESA; correct iron deficiency (IV iron preferred).
• TPO-RAs (romiplostim) now supported for CIT to preserve dose intensity in solid tumors.
• Sargramostim niche: post-auto SCT engraftment, acute radiation syndrome (adjuvant melanoma E4697 negative).