Radiobiology 2016

1/03/2016

Early versus late reactions Early reactions

Late reactions

Latency (Time to onset of clinical manifestion)

<90 days after onset RT; typically 3-9 weeks Not influenced by dose, but severity and duration of damage are dose-dependent Low (high α/β ~ 6-10 Gy) Shorter OTT leads to greater injury Typically transient, but consequential late reactions may occur

>90 days after onset RT; typically 0,5-5 years Inversely dependent on dose: higher dose leads to shorter latent period High (low α/β ~ 1-5 Gy)

Fractionation sensitivity

Influence of overall treatment time (OTT) Clinical course

No significant influence

Progressive and irreversible Compensation may occur Rehabilitation or treatment for complications may relieve

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Relevant factors

• Organs in the irradiated volume • Normal tissue constraints • Pathogenesis of functional tissue (L1.7) • Vascular component • Connective tissue • Specific functional tissue compartments • Previous irradations • Retreatment tolerance (L4.5)

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