SU‐E‐T‐633: Hypofractionated Prostate Treatment in a Single VMAT Arc

Purpose: Several publications have proposed during the last years hypofractionated treatment schedules in prostate cancer. Such schedules have been possible because the α/ß ratio for prostate carcinoma is comparable to, and even lower than, the surrounding late‐responding normal tissues. This work shows the scheme adopted in our institution for hypofractionated prostate cancer treatment and plan evaluation based in DVH parameters. Methods: Monaco 3.10 (CMS, Elekta) is the inverse planning system used for volumetric‐modulated arc therapy (VMAT). Treatments are delivered with an Elekta Synergy linac. Daily cone‐beam CT corrections are performed as image‐guided radiation therapy technique. The fractionation schedule, with the assumption that α/ß = 1.5 for targets and 3.0 Gy for OARs, consists on 28 fractions, delivering 2.5 Gy to prostate gland, 2.0 Gy to seminal vesicles and 1.8 Gy if lymph nodes are included. Dose‐volume constraints are taken from QUANTEC reviews and they are adapted to our fractionation scheme according the linear‐quadratic model (assuming the previous α/ß ratios): V45.4