Personalization of External Beam Radiation Therapy in Localised Tumours

This study is testing personalized external beam radiation therapy — where MRI imaging is used to better tailor and target radiation doses for people with early-stage prostate or breast cancer, aiming to deliver more precise radiation to the tumor while sparing healthy tissue. **You may be eligible if...** - You have early-stage localized prostate cancer (clinical stage T1-T2, no spread) OR early-stage breast cancer (unifocal ductal carcinoma, stage T1-T2 N0) - You are 18 or older with good general health (ECOG 0-2) - You have no contraindications to MRI - You are scheduled for active treatment (surgery, cryoablation, or radiotherapy) **You may NOT be eligible if...** - Your cancer has spread to lymph nodes or distant sites - You have had previous invasive cancer in the past 3 years - You have a mental disorder that prevents valid consent - For breast patients: you have bilateral breast cancer, a high-risk genetic mutation, or previously had chest radiation - For breast patients: you are male Talk to your doctor to see if this trial is right for you.