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Dose dE-eScalaTion IN prostATe radIOtherapy usiNg an MR-Linac in 2 Fractions (DESTINATION 2): protocol for a randomised, phase II/R-IDEAL2b trial

Cooper S, Alexander S, Breitkreutz D, Casey F, Christodouleas J, Dassen MG, Dell'acqua V, Dunlop A et al.

BMJ open, 2026

200 participants

Abstract

Introduction: Stereotactic body radiotherapy (SBRT) delivered on an MRI-guided linear accelerator (MR-linac) enables highly conformal prostate cancer irradiation. The DESTINATION 2 trial is a federated, randomised phase II/R-IDEAL 2b study evaluating whether de-escalating the dose to prostate tissue, while maintaining a high dose to MRI-visible tumour(s) in two fractions, reduces genitourinary (GU) treatment-related adverse events (AE) without compromising disease control in men with localised prostate cancer.

Methods: 200 men worldwide with localised, MRI-visible prostate cancer will be randomised 1:1 to receive either (1) prescribed uniform dose MR-linac SBRT (27 Gy in two fractions to the whole prostate and seminal vesicles with 0 mm CTV-PTV margin) or (2) de-escalated SBRT (20 Gy in two fractions to whole prostate with 0 mm CTV-PTV margin and 27 Gy in two fractions to MRI-visible tumour(s) with a 4 mm intraprostatic margin applied to the GTV. All treatments are delivered using MRI-guided adaptive Radiotherapy (MRIgRT). The primary endpoint is the absolute and relative risk reduction in acute grade 2+GU AE (CTCAE v5) within 12 weeks of completing radiotherapy. Secondary endpoints include late GU AE, acute and late gastrointestinal (GI) AE, sexual AE, patient-reported outcomes, dosimetry, technical feasibility and 2-year biochemical relapse-free survival.

Ethics and dissemination: This is a federated trial design in which each centre operates independently with its own…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 200 participants or records.

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