Definition
- Reduction in bone marrow activity → decreased production of one or more blood cell lines:
- Leukopenia/neutropenia → infection risk
- Anemia → fatigue, tissue hypoxia
- Thrombocytopenia → bleeding risk
Common Causes
- Chemotherapy: alkylating agents, platinum drugs, antimetabolites, topoisomerase inhibitors, taxanes, anthracyclines
- Targeted therapy & immunotherapy: some TKIs, BCL-2 inhibitors, CAR-T therapy
- Radiation therapy (bone marrow exposure)
- Bone marrow disorders: MDS, aplastic anemia
Clinical Manifestations
| Blood Line | Key Clinical Signs | Lab Thresholds |
|---|---|---|
| Neutrophils | Fever, infections, sepsis | ANC < 1,500/μL (mild), <500/μL (severe) |
| RBC | Fatigue, dyspnea, pallor | Hb <10 g/dL (clinically relevant) |
| Platelets | Petechiae, bruising, mucosal bleeding | Plt <50,000/μL (moderate), <20,000/μL (severe) |
Monitoring
- CBC with differential: baseline, pre-cycle, weekly if high-risk chemo
- Clinical assessments: signs of infection, bleeding, fatigue
- Renal/hepatic function: dose adjustments for some drugs
Supportive Care
- Neutropenia
- G-CSF (filgrastim, pegfilgrastim) prophylaxis if high-risk regimens
- Infection prevention: hand hygiene, prophylactic antibiotics in select patients
- Anemia
- RBC transfusions, ESA therapy (erythropoiesis-stimulating agents) per guidelines
- Thrombocytopenia
- Platelet transfusions if <10–20 × 10^9/L or bleeding
- Avoid NSAIDs, anticoagulants unless necessary
Clinical Pearls
- Timing of nadir is drug-dependent (commonly 7–14 days post-chemotherapy)
- Combination regimens → additive myelosuppressive effects
- Dose adjustments or cycle delays may be required to prevent severe toxicity