| Schedule | Constraint | Source |
|---|---|---|
| Conventional fractionation 70 Gy / 35 fx definitive · 60–66 Gy / 30–33 fx post-op | Max ≤45 Gy (ideal), ≤50 Gy (acceptable) | QUANTEC spinal cord, Lee 2019 NPC guideline, GORTEC 2004-03, Emami 2013 |
| PRV max ≤50 Gy | RTOG 0920 |
Quoted from eviQ 5049, checked 2026-09-24. Full table with references →
The spinal cord runs within the vertebral (spinal) canal from the medulla oblongata at the foramen magnum down to the conus medullaris in the upper lumbar spine. It is surrounded by cerebrospinal fluid and the thecal sac, all enclosed by the bony canal.
The spinal cord carries signals between the brain and the body — for movement, feeling and reflexes.
The cord behaves as a serial organ: damage to a short segment can interrupt function below it. Radiation myelopathy is rare but severe and irreversible, so cord limits are usually expressed as a maximum or near-maximum dose rather than a mean. In lung SBRT the cord is seldom close to a peripheral tumor, but paraspinal and posterior tumors can bring it into play, and it is routinely evaluated in conventionally fractionated thoracic plans. In breast treatment it matters only when the supraclavicular nodes are treated, and the cord would not be expected to come near its limit. In head and neck treatment the cord runs directly behind the neck targets along the whole length of the field, so it is evaluated in every plan, usually together with a planning risk volume. In brain treatment the upper cord matters for posterior fossa targets and for the lower edge of whole-brain and glioma fields; radiosurgery sources define it as the whole bony canal. In GI treatment the cord is evaluated for esophageal and pancreatic plans, where posterior beams pass close to it, and for liver SBRT near the spine.
In cervical cancer the cord is evaluated only when the para-aortic nodes are treated; pelvic fields stay below it.
For head and neck cases, Brouwer 2015 contours the true spinal cord, not the spinal canal:
Definitions differ between sources. For nasopharynx cases, Sun 2014 contours the visible true cord from the foramen magnum to 2 cm below the lower edge of the head of the clavicle, excluding the subarachnoid space. Some sources use the bony spinal canal instead. A limit only makes sense on the structure it was written for, so check the definition in the source behind your limit. Many clinics also add a PRV.
Consensus CT delineation guidelines for head and neck organs at risk from eight cooperative groups, with anatomical descriptions and example images. Citation checked against Crossref; content not yet reviewed by DoseLab.
Compares published contouring methods for the temporal lobe, middle and inner ear, parotid gland and spinal cord in nasopharynx cancer, recommends one method for each (Table 3), and provides a CT–MRI atlas of 33 organs at risk. Citation checked against Crossref; the temporal lobe and spinal cord recommendations were read in the open-access full text.