Prostate cancer (PCa) is the second most common malignancy in men worldwide. Radiotherapy (RT) is a well-established management option that contributes significantly to the treatment of PCa. Over the past 3 decades, significant advancements in RT have led to improvements in both efficacy and toxicity profiles, by virtue of several sequential and parallel technological developments. These innovations include the use of intensity modulated radiotherapy, improvements in image guided radiotherapy to minimize interfraction motion,1 techniques to manage intrafraction motion,2 the ability to deliver focal microboosts,3 and the ability to perform aggressive margin reduction.4 This enables steep dose gradients and more precise radiation therapy planning and delivery.

In the context of prostate cancer, adaptive RT (ART) is an emerging technique that allows for radiation treatment plans to be re-optimized based on interfraction changes in both target anatomy and organ-at-risk (OAR) anatomy. By mitigating the potential effects of these day-to-day deformations, ART offers the potential to minimize treatment-related toxicity, escalate the target dose, or both. Magnetic resonance (MR) and computed tomography (CT) imaging have played pivotal roles in ART by providing detailed anatomical and functional insights for treatment planning and real-time guidance. This review explores the technical principles, clinical applications, and technological developments of ART in managing PCa, highlighting their potential to optimize treatment delivery, reduce toxicity, and improve therapeutic outcomes. Three different modalities exist for ART: CT-guided, MR-guided, and positron emission tomography (PET)-guided approaches. However, this review will focus on CT- and MR-guided ART, as PET-guided ART is not widely used in PCa treatment at the time of this writing.