Omission Of Mri For Treatment Planning Does Not Affect Long-Term Outcomes After Prostate Sbrt.

Stereotactic Body Radiation Therapy (SBRT) is increasingly being used to treat men with localized prostate cancer. Diagnostic MRI imaging as well as MRI-guided treatment for these patients have become widely utilized. A minority of patients are not candidates for MRI imaging due to pre-existing conditions or patient intolerance. To our knowledge, this is the largest series to investigate long-term outcomes in men for whom MRI imaging is not employed as a component of their prostate SBRT treatment. A total of 2775 patients with localized prostate cancer were treated with inhomogeneous-dosed SBRT at an academic institution between April 11, 2006 and November 23, 2019. By NCCN categorization, patients were treated for low (29.6%), favorable intermediate (26.0%), unfavorable intermediate (34.9%), and high risk (9.6%) disease. The majority (84.0%) of patients were treated with a median dose of 3500cGy (3500-3625) over 5 fractions. Androgen deprivation Therapy (ADT) was prescribed in 17.1% of cases. Disease Free Survival (DFS) was scored using the “nadir + 2” definition and long-term urinary and rectal toxicity was characterized as occurring ≥6 months post radiation. Correlation analyses were performed using the Pearson Chi-Square test. Estimates for DFS and toxicity were determined using the Kaplan-Meier method. 132 (4.8%) patients in this series received treatment without a planning MRI, with the most common reason being a history of implanted defibrillator (46.2%). Those treated without an MRI were slightly older (69.8 vs. 67.2 years, p