# Organs at risk and dose constraints

Source: https://onco.cc/terms/organs-at-risk/  
OnCo record `organs-at-risk` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The healthy organs near a tumour that limit how much dose can be given, each with a maximum dose or dose-volume limit the plan must respect (for example, keeping the spinal cord below about 45 to 50 Gy).

## Summary

Every plan trades tumour dose against the tolerance of nearby organs: spinal cord, brainstem, optic nerves, lungs, heart, kidneys, rectum and bladder among them. Dose constraints come from decades of outcome data, summarised in the QUANTEC reviews and, for stereotactic treatment, HyTEC, and are expressed as maximum point doses or the volume allowed above a threshold. Meeting the constraints is what the optimiser and the planner negotiate.

## Fields

- Kind: Term
- Last checked: 2026-09-16
- Tags: radiation-wave1

## Sources

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

## Connected records

- technologies: [Adaptive radiotherapy (online replanning)](https://onco.cc/technologies/adaptive-radiotherapy/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [Radiotherapy treatment planning and QA software](https://onco.cc/technologies/treatment-planning-systems/), [Volumetric modulated arc therapy (VMAT)](https://onco.cc/technologies/vmat/)
- trials: [NRG CC001](https://onco.cc/trials/nrg-cc001/), [RTOG 0617](https://onco.cc/trials/rtog-0617/)

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JSON: https://onco.cc/api/v1/entities/organs-at-risk.json