Randomized MRI-Guided Prostate Boosts Via Initial Lattice Stereotactic vs Daily Moderately Hypofractionated Radiotherapy

The multiparametric-MRI (MP-MRI) defined Gross Tumor Volume (GTV) will receive 12-14 Gy on the first day of treatment and then the prostate plus proximal seminal vesicles (SV), the Clinical Target Volume (CTV)1, will receive 76 Gy in 38 fractions (Fxs) at 2.0 Gy per Fx. For High Risk patients, the distal SVs may be treated to 56 Gy in 38 Fxs or full dose (CTV2), and the pelvic lymph nodes may be treated to 56 Gy in 38 Fxs (CTV3).

The MRI defined GTV(s) will receive a higher dose per day than the CTV by dose painting. The GTV(s) will receive an absolute dose of 91.2 Gy. Assuming an α/β ratio of 3.0, this would be equivalent to 98.5 Gy in 2.0 Gy fractions. The prostate plus proximal seminal vesicles (CTV1) will receive 76 Gy in 38 fractions (Fxs) at 2.0 Gy per Fx. For High Risk patients, the distal SVs (CTV2) may be treated to 56 Gy in 38 Fxs or full dose, and the pelvic lymph nodes (CTV3) may be treated to 56 Gy in 38 Fxs.