Effects of Chemotherapy and Radiation on Myeloid Progenitor Cells

Mechanisms of Myeloid Progenitor Cell Damage

Chemotherapy and radiation primarily target rapidly dividing cells, including myeloid progenitor cells in the bone marrow, disrupting their proliferation and differentiation into mature neutrophils and other myeloid cells, as recommended by the National Comprehensive Cancer Network 1, 2
Radiation therapy, with or without chemotherapy, significantly reduces neutrophil counts by damaging myeloid progenitors, with effects that may be partially reversed by CSFs, according to the Journal of Clinical Oncology 3, 4

Severe neutropenia (neutrophil count <500/mm³) commonly occurs following myelosuppressive chemotherapy, increasing the risk of febrile neutropenia and potentially life-threatening infections, as reported by the Annals of Oncology and the National Comprehensive Cancer Network 5, 6
The incidence of febrile neutropenia ranges from 10-57% with standard chemotherapy regimens, with infection-related mortality up to 7%, according to the Annals of Oncology 5
Infants receiving chemotherapy are at particularly high risk for neutropenic morbidity due to the immaturity of their hematopoietic and immune systems, as noted by the Journal of Clinical Oncology 4

G-CSF (filgrastim) and pegfilgrastim are recommended (category 1) for prophylaxis of febrile neutropenia in high-risk patients receiving chemotherapy, as recommended by the National Comprehensive Cancer Network 7, 8
Initial doses of filgrastim should be administered 24-72 hours after completion of chemotherapy at 5 mcg/kg daily until post-nadir ANC recovery, according to the National Comprehensive Cancer Network 1, 9
Pegfilgrastim can be administered as a single 6 mg dose 24 hours after completion of chemotherapy given every 3 weeks, as recommended by the National Comprehensive Cancer Network 8, 9

CSFs should be avoided in patients receiving concurrent chemotherapy and radiation therapy, particularly involving the mediastinum, due to increased risk of thrombocytopenia and pulmonary toxicity, as reported by the Journal of Clinical Oncology and the Annals of Oncology 3, 4, 5
When CSFs are used with concurrent chemoradiation, there is a significant risk of increased thrombocytopenia and pulmonary toxicity, according to the Journal of Clinical Oncology 3, 4

For patients receiving chemotherapy with high risk of febrile neutropenia (≥20%), primary prophylaxis with G-CSF is recommended, as suggested by the National Comprehensive Cancer Network 8, 6
For patients receiving concurrent chemoradiation, avoid prophylactic CSF use due to increased risk of thrombocytopenia and pulmonary toxicity, as recommended by the Journal of Clinical Oncology and the Annals of Oncology 3, 4, 5
Monitor patients receiving G-CSF for potential side effects including bone pain, arthralgias, and myalgias, as noted by the National Comprehensive Cancer Network 7, 9