How Cancer Treatment Weakens the Immune System: Myelosuppression and Beyond

Many cancer therapies suppress immunity, increasing infection risk.

Mechanisms

1. Chemotherapy‑induced myelosuppression: Reduces neutrophils (innate) and lymphocytes (adaptive).
2. Corticosteroids: Inhibit T‑ and B‑cell function.
3. Targeted therapies: May deplete regulatory T cells, causing immune dysregulation.
4. Immunotherapy (checkpoint inhibitors): Can trigger autoimmune toxicity.
5. Radiation: Damages lymphocytes in the field.

Mitigation

• Growth factor support (G‑CSF)
• Prophylactic antimicrobials when indicated
• Vaccination timing (avoid live vaccines during immunosuppression)
• Close monitoring of counts and clinical status

Not all regimens cause equal suppression; oncologists tailor supportive care accordingly.