Radiotherapy Protocol for the management of SABR to the spine for 
Oligometastatic disease. 

 

Document revision History 

Version Number 

Date 

Document History. 

1.0 

22/11/22 

 Dr Sarah Taylor 

1.1 

April 22 

Verified through- LJ 

 

 

 

1.1 

09/06/23 

Ratified at NOG 



 

Radiotherapy Protocol for the management of SABR to the spine for Oligometastatic disease. ................ 1 
1. Treatments to include ...................................................................................................................... 2 
2. Indications for treatment ..................................................................................................................... 2 
3. Investigations required ................................................................................................................ 3 
4. Information given to patients .......................................................................................................... 2 
5. Consent ............................................................................................................................................. 3 
6. Trials Open ........................................................................................................................................ 3 
7. Position and immobilisation ............................................................................................................ 3 
8. Planning ............................................................................................................................................ 4 
8.1. Volume Definition: ............................................................................................................................ 4 
8.2. Planning............................................................................................................................................. 6 
9. Treatment ......................................................................................................................................... 8 
9.1. In vivo dosimetry as per local protocol ............................................................................................. 8 
9.2. Any other monitoring: ...................................................................................................................... 8 
9.3. On treatment imaging as per local protocols ................................................................................... 8 
9.4. For gaps in treatment follow local policy .......................................................................................... 9 
9.5. Follow up post SABR ......................................................................................................................... 9 
10. References ........................................................................................................................................ 9 


 


1. Treatments to include 

 Radical radiotherapy – SABR for oligometastatic disease to the spine 


 

2. Indications for treatment 

Inclusion criteria (all of the following criteria must be met, unless within a clinical trial): 

 Oligometastatic (defined as 1-3 extra-cranial metastatic lesions in total within a maximum of 2 
organs) histologically-proven malignancy with spinal metastasis on imaging 
 Not more than 2 consecutive spinal vertebral bodies involved or > 2 tumours within the spine 
 Tumour ideally 3-5mm from the cord 
 Well-defined lesion(s) on MRI imaging 
 Minimal interval from the primary treatment of 6 months and primary disease controlled 
 Neurosurgical opinion documented if SINS score >6 
 Absent, or potentially treatable extra-spinal disease 
 WHO performance status 0-2 
 Age ≥ 18 years 
 Life-expectancy >6 months 


Exclusion criteria: 

 Patients with spinal instability (SINS score 13-18) or unable to lie flat/tolerate treatment 
 Significant or progressive neurological deficit such that emergency surgery or radiation is 
required, including spinal cord compression or impingement 
 Disease free interval between primary treatment and manifestation of metastases of <6 months 
 Systemic anti-cancer therapy administered within 28 days of SABR, or planned for <28 days 
following treatment 
 Haematological primary malignancy such as lymphoma or myeloma 
 Pregnant or lactating females 
 Inability to comply with treatment requirements 
 Previous SABR to the same site 
 Untreated brain metastases (patients should have received SRS or resection) 


 

 

All potential Oligometastatic SABR patients should be discussed within a regional SABR MDT 
prior to treatment. 

 

 

 

 


Table 1: Spinal instability Neoplastic Score (SINS) System (adapted from Fisher et al): (1) 
https://doi.org/10.1186/1748-717x-9-69 

Component 

Score 

Location 

Junctional (O-C2; C7-T2; T11-L1; L5-S1) 

Mobile Spine (C3-6; L2-4) 

Semirigid (T3-10) 

Rigid (S2-S5) 

 

3 

2 

1 

0 

Mechanical pain 

Yes 

No 

Pain free lesion 

 

3 

2 

1 

 Bone Lesion 

Lytic 

Mixed (lytic/blastic) 

Blastic 

 

2 

1 

0 

Radiographic spinal alignment 

Subluxation/translation present 

Deformity (kyphosis/scoliosis) 

Normal 

 

4 

2 

0 

Vertebral body collapse 

>50% collapse 

<50% collapse 

No collapse with >50% body involved 

None of the above 

 

3 

2 

1 

0 

Posterolateral involvement 

Bilateral 

Unilateral 

None of the above 

 

3 

1 

0 



 

 

3. Investigations required 

 Histological confirmation of malignancy. Biopsy from malignancy not necessary if known primary 
cancer and MDT are in agreement that imaging is consistent with metastasis. 
 Diagnostic / staging imaging to include: 


-CT chest, abdomen and pelvis 

-MRI spine 

-PET-CT 

 


 Review of clinical history to include: 


Current symptoms including pain and neurological impairment, mobility and performance 
status. 

 Previous radiotherapy : 


Assess whether the patients had had previous radiotherapy, and if so, whether there is likely to 
be any overlap, which could affect ability to deliver treatment 

 Chronic conditions or disease that affects radiosensitivity: 


Ensure full assessment of past medical history, identifying conditions that may confer increased 
radiosensitivity or risk, affect delivery of radiotherapy or affect prognosis 

 Ongoing medication that may affect response to radiotherapy: 


Identify medications, which alter radiotherapy response. Stop potentially radiosensitising 
agents for a duration prior to and following SABR where possible. 

 Others as required: 


Analgesia should be prescribed if patients are experiencing pain. 

 

4. Information given to patients 

 Patients will have the rationale, technique and potential acute and long-term toxicities of spinal 
SABR discussed with them in a new patient or radiotherapy clinic. They should be provided with 
the appropriate information leaflet. 
 Patients should have also had the opportunity to discuss the risk and benefits of surgical 
intervention if they are potentially suitable. 
 It is important that patients are educated regarding the signs and symptoms of metastatic spinal 
cord compression and are given appropriate contacts. 


Pre-treatment preparation 

 Patients should be commenced on Dexamethasone 4mg OD starting the same day as SABR and 
finishing with the last SABR fraction. 
 Whilst on Dexamethasone patients should receive a PPI eg Lansoprazole 30mg 
 Patients should have a pain assessment and be prescribed adequate analgesia. If stomach or 
bowel is receiving significant dose, prescribe prophylactic anti-emetics +/- anti-diarrhoea agents. 


 

 

 

 


5. Consent 

Informed consent will be obtained by an IR(ME)R Practitioner ( with a minimum of FRCR part 1) at new 
patient/planning clinic. 

6. Trials Open 

Consider current trials open in any of the Radiotherapy centres in the East Midlands: 

SARON – synchronous Oligometastatic NSCLC. Radical RT (SABR or conventional RT) to the primary 
lesion +/- nodes and SABR to the oligometastatic disease. 

HALT – mutation positive NSCLC with oligoprogression vs continuation of the TKI 

 

7. Position and immobilisation 

All patients will be CT scanned as per local protocol 

 Patients should receive analgesia 30 minutes prior to planning scans (and subsequent 
treatments) if pain is present. 
 The 3D planning CT should include at least 10cm superior and inferior to the treatment volume. 
It should cover all relevant vertebral bodies and OARs (if part of the lung, liver or kidney is likely 
to receive a clinically significant dose, the whole organ must be included in the imaging as there 
are volumetric dose constraints). 
 Ideally 1mm slice thickness will be used with spacing 
 IV contrast is not required routinely, but can be used at the clinician’s request if it would aid 
OAR delineation 
 Centres should use the advanced scanner features to reduce image artefact produced in 
patients with metalwork 


Planning MRI 

 Patients should have a planning MRI scan performed in the treatment position with a flat table 
top and using the same immobilisation as the planning CT, if available. This should ideally be 
done on the same day as the planning CT. 
 It should cover one vertebra above and below the spinal abnormality, typical MRI length ~15cm. 
 T1 and T2 weighted axial images with contrast and 2mm slice thickness should be regarded as 
essential scans. T1 images are used for GTV delineation and T2 for cord. Consideration could 
also be given to T2 sagittal scans. T1_pre-Gad are unlikely to useful. 
 Subject to the patient’s comfort and compliance, a Spine Coil should be used for patients with 
metalwork (assuming spine flexion is locally prevented by the metalwork), but other coils 
(together with the flat table top) should be used for patients without metalwork. 


 


Immobilisation as per local protocol: 

 Due to the proximity of the spinal cord, it is crucial that patients are robustly immobilised. 
 T4 and above: Immobilise with customised head/shoulder support, indexed knee support, arms 
down 
 T5 and below: Immobilise with an indexed wingboard with arms elevated, custom body vacuum 
bag, knee and foot supports 


8. Planning 

8.1. Volume Definition: 

a) GTV (to be outlined in turquoise) = gross tumour using all available imaging 
b) CTV (to be outlined in violet) should contain GTV and include bony CTV expansion to account 
for subclinical spread. Include abnormal marrow signal suspicious for microscopic invasion. See 
diagram and table below for further details: 


Figure 1: Anatomic 
classification for 
consensus target 
volumes for Spine SABR 
(taken from SABR: A 
Resource V6.1) (2) 

 

Figure 2: Guidelines for 
SABR bony CTV 
delineation (taken from 
SABR: A Resource V6 ) (2) 


PTV_Prescribe
 Circumferential CTVs encircling the cord should be avoided except in rare circumstances 
where the vertebral body, bilateral pedicles/lamina, and spinous processes are all involved, 
or when there is extensive metastatic disease along the circumference of the epidural space 
without cord compression. 


 

c) PTV (use blue colour) = CTV plus 2-3mm depending on equipment and experience, use local 
audit data 
d) In order to allow for unavoidable under-dosing of the PTV in close proximity to the spinal cord, 
whilst maintaining consistency in the treatment prescription, a volume (PTV_Prescribe) should 
be created, which restricts the PTV by spinal cord PRV+2mm. If it is different from the PTV, this 
volume should be used for prescribing and additional dose reporting. 


 

Figure 3: Illustration of PTV_Prescribe volume (taken from SABR: A Resource V6.1) (2) 

 

i.e. PTV_Prescibe =PTV- (cordPRV+2mm) 

 PTV_Prescibe volume may be generated or edited appropriately in treatment situations where 
the GTV extends beyond this volume, with consideration given to the achievable dose gradient. 


 

e) Organs at risk (OAR) to be outlined: 
 Spinal dose constraints must be met. The spinal cord (SpinalCord) should be contoured using the 
fused T1 and T2 weighted MR scans and should extend to at least one vertebra superior and 
inferior to the PTV. At the level of the cauda equina, the thecal sac should be considered to 
represent the relevant OAR 
 A PRV margin will be generated to create SpinalCord_XX (where XX is the size of the margin in 
mm). This margin is for set-up error alone. In cases where good image quality allows confident 
co-registration and delineation, an isotropic margin of 2-3mm may be appropriate. However, if 
image quality is compromised, it is recommended that the larger volume of either a further 
1mm isotropical expansion or the thecal sac be used instead. 



 

 Any OARs which are traversed by a treatment beam should be contoured. Where OAR 
constraints are based on the dose received by the whole organ, the OAR should be outlined 
completely. Otherwise OARs should be contoured at least 2cm superiorly and inferiorly to the 
PTV for coplanar techniques. 
 OARs requiring delineation may include oesophagus, stomach, lungs, heart, kidneys, liver, 
bowel, thyroid, larynx, trachea, chest wall. 
 OARs should be outlined according to the Global Harmonization group consensus guideline (3): 
https://doi.org/10.1016/j.radonc.2020.05.038. Refer to the East Midlands lung/lymph node 
SABR protocols for OAR guidance for thoracic/lumbosacral lesions respectively. 


 

f) It is the responsibility of the clinical oncologist to outline and/or review all the OAR outlines 
specified above 
g) Ideally the ITV and OARs should be peer-reviewed by at least one other clinical oncologist 


 

8.2. Planning 

 

a) Prescribed dose: 
 There is little consensus in the literature regarding the optimal dose–fractionation, but the 
following have shown good outcomes with acceptable toxicity: 
o Preferred fractionation: 27Gy in 3# 
o If unable to meet dose constraints, reduce to 24Gy in 3# 
o Re-irradiation fractionation: 30Gy in 5#, however this needs to be considered on an 
individual patient basis to asses previous spinal cord doses delivered 
o Treatment should be delivered on alternative days with at least 40 hours between 
each fraction. The maximum interval between fractions is 4 days. 




 

b) Treatment should be prescribed so that 95% of the PTV (or PTV_Prescribe where appropriate) 
should be covered by the prescription isodose, unless there is a need to accept less coverage to 
achieve the OAR tolerances. 
c) Hot spots should be within the PTV and ideally 110-120% of the prescription dose, mandatory 
110-130%. 
d) Data from the CtE scheme found that R100% and R50% lose sensitivity to detect poor 
conformity with decreasing PTV coverage, therefore modified metrics with Prescription dose 
spillage (PDS) and Modified Gradient Index (MGI) need to also be calculated and reported as 
below: 


 


 

Prescription dose spillage = Vol (100%) 

 PTV V100% 

Modified Gradient Index = Vol (50%) 

 PTV V100% 

Definitions 

Vol(100%)/Vol(PTV) = ratio of prescription isodose volume to PTV 

Vol(50%)/Vol(PTV) = ratio of 50% prescription isodose volume to PTV 

Vol(100%) and Vol(50%) = volumes of the patient receiving at least 100% and 50% of the 
prescription dose respectively 

PTV V100% = the volume of the PTV receiving at least 100% of the prescription dose 

 

 

 

 

 

 

 

 

Prescription Dose Spillage (PDS) requirements: 

Vol(PTV) (cc) 

Vol(100%)/PTV V100% 

Target 

Tolerance 

Minor Deviation 

<20 

1.20 

<1.25 

1.25-1.40 

20-40 

1.10 

<1.20 

1.20-1.30 

>40 

1.10 

<1.15 

1.15-1.20 



 

Modified Gradient Index (MGI) requirements 

Vol(PTV) (cc) 

Vol(50%)/PTV V100% 

Target 

Tolerance 

Minor Deviation 

<20 

5.5 

7.5 

7.5-9.5 

20-40 

4.5 

6.0 

6.0-7.5 

>40 

4.5 

5.5 

5.5-6.5 



† above tables adapted from Stereotactic Ablative Body Radiotherapy: A Resource. UK SABR consortium. V6.1. 
2019. (2). Target values are based on median data from the CtE scheme and should be achievable for around half 
of patients. 


e) Dose constraints for OARs: The relevant anatomical SABR protocol should be referred to 
regarding constraints or refer directly to the UK 2022 Consensus on Normal Tissue Dose-Volume 
constraints for Oligometastatic Primary Lung, and Heptacellular Carcinoma Stereotactic Ablative 
Radiotherapy (5). https://doi.org/10.1016/j.clon.2022.02.010 


 

 If a patient is being treated within a clinical trial then the trial protocol overrides this protocol 
 If the patient is off protocol, this should be noted and the correct local procedure for recording 
off protocol treatments followed 


 

9. Treatment 

9.1. In vivo dosimetry as per local protocol 

9.2. Any other monitoring: 

Patients should be assessed for toxicity and new symptoms prior to each fraction. It is the 
responsibility of the treatment radiographers to carry out the review. Toxicity should be 
documented using the Common Terminology Criteria Adverse Events (CTCAEv4). 

 Side effects may include: 

 Acute: 
o All: Skin reaction, Tiredness, Pain flare, loss of appetite 
o C-spine: Mucositis 
o T-Spine : Oesophagitis, nausea, chest pain 
o L-Spine : Diarrhoea, nausea 


 

 Late: Increased risk of vertebral compression fracture or collapse, which could require 
surgical intervention, rib fracture, small long-term risk of trachea-oesophageal 
fistula/stricture formation, small risk of myelopathy or nerve damage, bowel damage, 
thyroid dysfunction ( depending on level) 


 

9.3. On treatment imaging as per local protocols 

 Use Hexapod/ equivalent if available 
 Daily 3D CBCT 
 Match to bone. Maximum acceptable shift 5mm, above this re-set-up/discuss with clinician. 
 For centres newly treating SABR, consider post treatment offline CBCT to confirm position – this 
can be reviewed and likely discontinued after the first 10 patients. 


 


9.4. For gaps in treatment follow local policy 

Treat as category 2 for gaps in treatment. Ensure 40 hours between treatments. 

 

9.5. Follow up post SABR 

 Patients should be assessed for acute toxicity 4 weeks post SABR 
 Subsequently patients should be reviewed at 3, 6 and 12 months post SABR, then annually 
thereafter, but will depend on the underlying primary cancer diagnosis and disease status. 
Follow-up following the first post radiotherapy visit should be with the primary site team. 
Review should include assessment of toxicity (using CTCAEv4) and symptom review (including 
pain). 
 The first post-treatment CT (typically CAP) should be done at 3 months and then repeated as 
determined by the patient’s primary oncology team. 


 

 

10. References 

 

1. Fisher C, Schouten R, Versteeg a et al. Reliability of the Spinal Instability Neoplastic Score (SINS) 
among radiation oncologists: an assessment of instability secondary to spinal metastases. Radiat 
Oncol. 2014 Mar 4;9:69. 
2. Stereotactic Ablative Body Radiation Therapy (SABR): A Resource. Version 6.1. UK SABR Consortium. 
Jan 2019. 
3. Organ at risk delineation for radiotherapy clinical trials: Global Harmonization Group consensus 
guidelines. Radiation and Oncology. 2020. 150; 30-39. 
4. Stereotactic Ablative Radiotherapy for Oligometastatic Non-small cell lung cancer a Randomised 
Phase III Trial – Radiotherapy and QA guidelines V3.1. April 2021. 
5. P. Diez, G. Hanna, K Aitken et al. UK 2022 Consensus on Normal Tissue Dose-Volume Constraints for 
Oligometastatic, Primary Lung and Hepatocellular Carcinoma Stereotactic Ablative Radiotherapy. 
Clinical Oncology. 2022.