SBRT 2016

Radiobiology

 SBRT involves the application of high fractional doses in a range not studied in prior decades  Conversion of physical dose to biologically equivalent dose (e.g. in 2-Gy fractions)  Derived from linear-quadratic model which may not describe all tissue effects  Uncertainty in a / b parameter:  Prostate: 4 x 9.5 Gy ( a / b = 2 ± 1 Gy) => 109 (95 – 133) Gy  Uncertainty in normal tissue tolerance (small volumes; high doses)  Wide variation on fraction duration, overall treatment time, prescription isodose line: 50-80% (high dose regions inside tumor)

Stereotactic body radiation therapy: The report of AAPM Task Group 101