Physics Bucharest 2017

Interplay effect: Lung cancer

 Studies show that interplay effect can alter the dose distribution of a single fraction , but not a fractionated course of treatment.  Dose variation (Jiang et al. )

1 fraction, 1 field: 30% 1 fraction, 5 fields: 18% 30 fractions: 1-2%

 SABR : interplay effect is negligible , effects are averaged out due to • larger number of MU • increased treatment time

Potential risks: interplay effect

 Strategies to reduce interplay effect: • ↑ n ° of arcs •

↓ dose rate  prolonging treatment time • avoid MLC motion perpendicular to the tumor motion.

Chan JTO 2014, Jiang Phys Med Biol 2003