Freedom to choose the right approach for every patient

Adaptive radiotherapy (also known as ART or Adaptive Radiation Therapy) adjusts treatment to each patient’s anatomy and tumor response. There are two main ways of adapting treatment plans: offline, where the plan is adapted in between sessions, or online, where the plan is adapted in between sessions, or online, where the plan is adapted immediately prior to treatment or during treatment whilst the patient remains on the treatment couch.

Online adaptive radiotherapy is a treatment approach that adapts the radiation plan in real-time based on the patient’s anatomy at the time of treatment. Unlike traditional radiotherapy, which uses a static reference plan created before the first fraction, online adaptive radiotherapy uses onboard imaging (e.g. MRI or CBCT) to visualize the anatomy of the day and anatomical changes, such as tumor shrinkage or organ motion and adapt the plan accordingly. This ensures more precise targeting and better sparing of healthy tissue for more personalized treatments.

Online adaptive radiotherapy demands high-quality daily imaging, whether via CBCT or MRI, to clearly visualize the target and organs at risk (OARs). This level of imaging is essential to assess daily anatomical changes and determine whether plan adaptation is necessary. Moreover, crisp, highly detailed imaging is required for AI-driven auto-segmentation to support consistent, reproducible adaptation and to enable fast workflows.

In short, high-quality imaging isn’t just a component of online adaptive radiotherapy; it’s what makes it possible.

The emergence of online adaptive therapy on CT-Linacs significantly broadens access to Adaptive radiotherapy (ART), making it feasible for more clinics and more patients. However, this does not replace the unique value of MRgRT, it complements it.

This hybrid model mirrors the diagnostic imaging world, where clinicians choose the modality that best suits the clinical question. In the same way, radiation oncologists will select between CT and MR guidance based on tumor site, motion characteristics, and clinical goals.

CT-guided ART is highly effective for many common indications, such as prostate, bladder, lung and pelvic lymph nodes, where anatomical structures are clearly visible on CT. These systems offer fast workflows that resemble conventional IGRT workflows and are ideal for high-throughput environments.

MRgRT, on the other hand, remains indispensable for more challenging cases where soft tissue contrast, real-time imaging, or functional imaging is critical. For example, in liver, pancreas, or rectal cancers, MRgRT enables visualization of structures that are poorly defined on CT, or in cases with mobile tumors, Elekta Unity with real time motion monitoring allows safe delivery of ablative doses.

No, with Elekta Linacs online adaptive is a workflow, not a system. With Elekta ONE® Online, adaptive radiotherapy is accessible on versatile C-arm Linacs, with full flexibility to decide per fraction whether adaptation is beneficial, or whether a standard IGRT workflow can be followed.

Elekta ONE Online is also available as an upgrade for Evo and Versa HD® systems, expanding access to adaptive radiotherapy without requiring the purchase of a new Linac.

The duration varies depending on the treatment modality (MR-Linac or CT-Linac) and complexity of the case. On Evo with Elekta ONE Online, adaptive sessions typically fit within standard treatment slots. For prostate and bladder cases, clinicians report completing the full workflow, from setup to delivery, in under 20 minutes. As the plan can be optimized to the anatomy of the day, clinicians report fewer instances of repositioning or sending patients to empty their bladder.

Treatments with Elekta Unity for prostate, oligometastatic, and brain cases typically fit within 30-minute slots, while more complex treatments, such as pancreas or liver SBRT with gating and ablative doses, may require up to 45 minutes. These longer sessions should be considered in the context of Unity’s high SBRT adoption (>55%) and widespread use of hypofractionation, which significantly reduces the total number of treatment sessions required.

Offline adaptive radiotherapy allows clinicians to assess anatomical changes between fractions and replan when needed, without the time pressure of adapting the plan during a treatment session. This is particularly useful for cases with gradual anatomical changes or when workflow constraints make online adaptation impractical.

With Elekta Evo and Elekta ONE Planning, offline adaptation becomes significantly faster and more accessible. With Iris® high-definition, AI-enhanced imaging enables immediate visualization of target boundaries and organs-at-risk. Advanced analysis tools support rapid plan assessment, and when re-planning is required, GPU-based dose calculation and optimization deliver adapted plans within minutes.

This streamlined workflow reduces the burden traditionally associated with offline adaptation, making it easier to implement and allowing more patients to benefit from personalized treatment. With Elekta ONE Online, clinicians can flexibly choose between online and offline adaptation based on clinical need, patient anatomy, and departmental resources.

The MR-Linac Consortium and the CT-Linac Adaptive Consortium play a pivotal role in driving the clinical adoption of online adaptive radiotherapy by fostering a collaborative, evidence-based ecosystem. These consortia bring together early adopters, clinical experts, and Elekta’s product teams to share best practices, establish clinical evidence, and co-develop future solutions.

Through regular collaboration, clinicians gain practical insights and mentorship that support successful integration of Adaptive radiotherapy into daily practice, whether on Elekta Unity or CT-Linac systems.