Magnetic Resonance Imaging-guided Focal Boost to Intraprostatic Lesions Using External Beam Radiotherapy for Localized Prostate Cancer: A Systematic Review and Meta-analysis

Context: It is anticipated that a focal boost to intraprostatic lesions (IPLs) using external beam radiotherapy (EBRT) guided by magnetic resonance imaging (MRI) will increase biochemical disease-free survival (bDFS) without increasing toxicity in the treatment of localized prostate cancer (PC).Objective: To systematically review clinical outcomes for MRI-guided EBRT focal boost to IPLs.Evidence acquisition: Three independent reviewers conducted literature searches in three databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. The inclusion criteria were original English-language arti-cles from 2000 to 2021 on prospective studies of patients with localized PC (n > 10) receiving an MRI-guided EBRT focal boost to IPLs. The main outcomes and measures were safety, gastrointestinal (GI)/genitourinary (GU) toxicities, quality of life, and bio-chemical disease outcomes. Weighted random-effects meta-analyses were conducted. Heterogeneity was assessed using the I2 statistic. Publication bias was assessed via fun-nel plots.Evidence synthesis: Seventeen studies (1290 patients) were included. There were heterogeneities in patient risk category (low risk, 63; intermediate risk, 532; high risk, 695), MRI utilization, and treatment planning and delivery. All studies reported good safety, with estimated rates of 7.5%/7.0% (95% confidence interval [CI] 4.0-12.1%/2.8-1 2.8%) and 0.1%/0.2% (95% CI 0-0.4%/0-1.1%) for acute/late cumulative grade >= 2 and grade >= 3 gastrointestinal toxicities, and 29.5%/16.0% (95% CI 17.6-43.0%/8.3-25.7%) and 0.4%/1.3% (95% CI 0.0-1.3%/0.3-3.0%) for acute/late grade >= 2 and grade >= 3 geni-tourinary toxicities, respectively. Across patients in focal boost studies with follow-up >5 yr, bDFS was 92.4% (95% CI 84.5-97.7%). The overall bDFS was 95.0% (95% CI 91.9- 97.4%) regardless of follow-up duration.Conclusions: MRI-guided EBRT focal boost to IPLs in localized PC was feasible and safe, with low GI/GU toxicities and favorable biochemical disease outcomes. Level 1 evidence supports the superior bDFS of this approach over whole-prostate irradiation for standard fractionation; however, further research is required for hypofractionation and ultrahypofractionation.Patient summary: We reviewed 17 studies on the use of magnetic resonance imaging (MRI)-guided radiotherapy with delivery of a higher radiation level to lesions within the prostate that were visible on MRI. This approach was well tolerated and might offer better disease control in prostate cancer over traditional radiotherapy.(c) 2022 The Author(s). Published by Elsevier B.V. on behalf of European Association of Urology. This is an open access article under the CC BY license (http://creativecommons.