A recent dosimetric inquiry suggested planning target volume (PTV) margins could be reduced from the standard 7 mm to as little as 3 mm for intact prostate radiation if online adaptive planning was used (i.e., intrafraction movement was almost always encompassed by a 3 mm margin). This study takes it a step further by verifying tighter margins on 65 simulated Varian Ethos adaptive radiation treatments. They determined that the sweet spot was PTV margins of 4 mm on the prostate and 5 mm margins on the seminal vesicles during daily adaptive radiation with verification CT, which actually resulted in superior clinical target coverage than standard static 7 mm PTV margins. | Byrne, Adv Radiat Oncol 2023
