Hematological Toxicity of Hypofractionated Radiotherapy: A Review of the Available Evidence.

Hypofractionated radiotherapy is commonly used to treat many cancers. The number of indications for this fractionation schedule is increasing. Knowledge of the potential hematological toxicity arising from hypofractionated irradiation is vital since many patients receive further systemic treatment. This review analyzes the available evidence on the effect of hypofractionated radiotherapy on hematological toxicity. However, radiobiological data on bone marrow responses to high doses of radiation per fraction are sparse. Additional biological effects may also play an significant role in bone marrow function and recovery after hypofractionated radiotherapy. Clinical data show a good early hematological tolerance of hypofractionated radiotherapy (both large field and for stereotactic body radiotherapy). There are, however, no data available that assess late hematological toxicity. Evidence on acute hematological toxicity after hypofractionated radiotherapy does not suggest any significant impact of altered fractionation on early treatment tolerance, although further research to assess this problem is needed. The effect of hypofractionation on late hematological tolerance is unknown because the data are still lacking.