# Adaptive radiotherapy (online replanning)

Source: https://onco.cc/technologies/adaptive-radiotherapy/  
OnCo record `adaptive-radiotherapy` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Re-shaping the treatment plan to the anatomy of the day, using the images taken on the treatment couch, so the dose follows a shrinking tumour or a moving bladder.

## Summary

Conventional radiotherapy delivers a plan drawn on one planning scan for the whole course, even though tumours shrink, weight changes and organs move. Adaptive radiotherapy re-contours and re-optimises the plan, either between sessions (offline) or on the couch in minutes (online) using cone-beam CT or MRI with AI-driven contouring. The MR-linac and CT-based systems such as Ethos made daily online adaptation practical from around 2019, and trials in bladder, cervix, head and neck and lung cancer are testing whether the tighter margins reduce side effects.

## Fields

- Kind: Technology
- Status: emerging
- Last checked: 2026-09-17
- Tags: radiation-wave1
- Principle: Daily imaging, automated re-contouring and rapid re-optimisation produce a new plan matched to that day's anatomy before the beam is delivered.
- Since: 2010
- Strengths: Smaller safety margins; Follows tumour shrinkage; Fewer doses to moving organs
- Limitations: Adds time to each session; Depends on fast, reliable auto-contouring; Benefit still being measured in trials

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Adaptive_radiation_therapy

## Connected records

- fronts: [Radiation Therapy](https://onco.cc/fronts/radiation/)
- technologies: [AI auto-contouring and adaptive planning](https://onco.cc/technologies/auto-contouring-ai/), [Dose painting and biologically guided radiotherapy](https://onco.cc/technologies/dose-painting/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight)](https://onco.cc/technologies/in-room-imaging-systems/), [Knowledge-based and automated treatment planning](https://onco.cc/technologies/knowledge-based-planning/), [MR-guided adaptive radiotherapy](https://onco.cc/technologies/mr-linac/), [Oncology information and record-and-verify systems (ARIA, MOSAIQ)](https://onco.cc/technologies/oncology-information-systems/), [Proliferation-invasion (reaction-diffusion) models of glioma](https://onco.cc/technologies/reaction-diffusion-glioma-model/), [Radiotherapy treatment planning and QA software](https://onco.cc/technologies/treatment-planning-systems/), [Ring-gantry linacs (Halcyon, Ethos)](https://onco.cc/technologies/ring-gantry-linac/)
- terms: [GTV, CTV and PTV (target volumes)](https://onco.cc/terms/planning-target-volume/), [Organs at risk and dose constraints](https://onco.cc/terms/organs-at-risk/)
- trials: [Adaptive Boost Radiotherapy to Primary Lesions and Positive Nodes in the Neoadjuvant Treatment of Locally Advanced Rectal Cancer](https://onco.cc/trials/nct06246344/), [Moderated Hypofractionated Online Adaptive Radiotherapy in Cervical Cancer](https://onco.cc/trials/nct06641635/), [Response Adaptive Radiotherapy Following Immunotherapy-based Induction for Non-HPV Related HNSCC](https://onco.cc/trials/nct06345287/)
- cancers: [Hypopharyngeal cancer](https://onco.cc/cancers/hypopharyngeal-cancer/), [Laryngeal and hypopharyngeal cancer](https://onco.cc/cancers/laryngeal-cancer/), [Oropharyngeal cancer (tonsil and base of tongue)](https://onco.cc/cancers/oropharyngeal-cancer/)
- companies: [ViewRay (MRIdian)](https://onco.cc/companies/viewray/)

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