Target volume delineation of lung
cancer
By
Dr. Mohamed Saad El Deen
Lecturer of Clinical Oncology and
Nuclear medicine
Outlines:
• Radiological anatomy.
• Target volume delineation.
- Locally advanced disease.
- P.O.R.T
• Organs at risk.
Radiological anatomy
• Carcinomas of the lung originate from the pulmonary
parenchyma or the tracheobronchial tree .
• The mediastinum lies in the central region of the
thorax and contains the heart, great vessels,
esophagus, and regional lymph node levels.
Level of thoracic inlet
Vessels are SVC , brachiocephalic , LCC , aorta
Level of great vessels
level of arch of aorta
level above level of pulmonary trunk
- azygos vein
Level of pulmonary artery division
Level of the heart
1- RT atrium 2- LT atrium 3 – RT ventricle 4LT ventricle 7 – IVC
CT chest , pulmonary window , coronal
reconstruction
Show level of division of trachea.
Lymph nodes of mediastinum
(MD-ATS)
1- supraclavicular L.N : low cervical , supraclavicular , sternal
notch node from lower margin of cricoid to the clavicle and
upper border of manubrium
2- RT and LT upper paratracheal
- RT extend from upper border of manubrium to the
intersection of caudal margin of innominate vein with the
trachea.
- LT extend from from the upper border of manubrium to the
superior border of aortic arch.
3- 3A: Pre-vascular :they are anterior to the vessels.
3P :Pre-vertebral behind the esophagus .
4- RT and LT lower paratracheal L.N :
- RT lower paratracheal L.N extend from intersection of
the caudal margin of innominate vein with the trachea to
the lower border of the azygos vein..
- LT Lower Paratracheal extend from upper margin of the
aortic arch to the upper rim of the left main pulmonary
artery.
5- Subaortic: these nodes are located lateral to the ligamentum
arteriosum. they are not
located between the aorta and the
pulmonary trunk but lateral to these vessels.
6- Para-aortic: they are lying anterior and lateral to the ascending
aorta and the aortic arch .
7-Subcarinal
8- Paraesophageal Nodes below carina.
9- Pulmonary Ligament Nodes lying within the pulmonary
ligaments.
10- Hilar nodes: These include nodes adjacent to the main stem
bronchus and hilar vessels.
- On the right they extend from the lower rim of the azygos
vein to the interlobar region.
- On the left from the upper rim of the pulmonary artery to the
interlobar region.
1- sternal notch node
2- RT upper paratracheal L.N
3A :small perivascular node
The arrow point to 3A prevascular node
4 R :RT lower paratracheal node
6 Para aortic node
This level above level of pulmonary trunk
4R :RT lower para tracheal L.N
4L :LT lower paratracheal L.N
3A :prevascular node
5 : subaortic nodes
This cut is blew the other cut at the level of pulmonary trunk with
the same L.N
10- hilar nodes
7 : subcarinal nodes to the RT of oseophaguse
10- hilar nodes
This image below level of the carina
8- paraoesophageal nodes to the RT of the oesophagus
Diagnostic Workup Relevant
for Target Volume Delineation
Target volume delineation is dependent on:
• computed tomography (CT) scan of the chest with
contrast .
• (PET)/CT imaging .
• Mediastinoscopy or endobronchial
ultrasound(EBUS).
• On CT scan with contrast, we consider lymph nodes
measuring at least 1 cm in shortest diameter are to be
positive radiographically for malignant involvement.
• PET imaging provide upstaging in approximately 15–
30 % of patients and distinguish atelectasis from
tumor.
Staging
Simulation
• Patients are typically immobilized with their arms
over their head to maximize the number of potential
beam angles.
• CT simulations are performed with a slice thickness
of 2.5–3 mm
• Four-dimensional (4D) CT scans are acquired, to
account for internal motion.
• When the magnitude of respiratory motion is <1 cm
and regular, patients are treated with a“freebreathing” approach.
• If irregular or motion >1 cm, then respiratory management is
considered, either deep breathhold (inspiratory or expiratory)
or respiratory gating, in which radiation is delivered at specific
periods of the breathing cycle.
• For patients to tolerate the deep breath hold
technique, they need to be able to maintain the
appropriate position in the respiratory cycle for at
least 15 s.
• Tumors located in the superior portion of the lung
typically have reduced motion compared to inferior
tumors in closer proximity to the diaphragm.
• Similarly, larger tumors have been shown to have
reduced motion during breathing.
Target Volume Delineation
Locally advanced disease
• An involved field approach is used for target volume
delineation, due to the published low likelihood of
disease recurrence in elective lymph nodes.
• An involved field technique plus inclusion of the
ipsilateral hilum is also now recommended in
(RTOG’s) recent randomized trial (RTOG 0538).
• Gross tumor volume (GTV) – gross disease,
including primary tumor and lymph nodes.
Definition of GTVN
GTVN should include
–1. any hilar or mediastinal lymph nodes ≥ 1 cm in short axis.
–2. any nodes with
abnormal findings detected on
bronchoscopy and/or mediastinoscopy.
–3. two or more nodes clustered in the high risk nodal
stations.
–4. any visible nodes at the 1st echelon or within 1cm
proximity to the primary tumor.
• Clinical target volume (CTV) – gross disease +
region at risk for microscopic spread .
• This volume often includes the remainder of the
involved lymph node station.
• This volume is also edited to respect anatomical
boundaries(taken off of bones, arteries, etc.)
• Internal target volume (ITV) – clinical target volume
+ respiratory motion.
• Planning target volume (PTV) – ITV + daily setup
variation.
Two different methods of target delineation, accounting for respiratory motion.
( Top ) Standard volumes that take into account tumor
motion, with ICRU definitions. ( Bottom ) Variation used at MDACC in select
patients
• Involved field techniques, incorporation of tumor
motion, and guidelines for delineating target volumes
based on available imaging (GTV, CTV, ITV) do not
differ between locally advanced NSCLC and SCLC.
• GTV-to-CTV margins of 0.5–1.0 cm are considered
acceptable.
• CTV to PTV = 5 mm.
• For
patients
who
have
undergone
induction
chemotherapy with a reduction in tumor size:
– Parenchymal lesions: target post-chemotherapeutic
volume with GTV; coverage of pre-chemotherapeutic
volume with CTV.
– Involved lymph nodes: post-chemotherapy volume
covered with GTV, entire nodal station covered with
CTV.
• With SCC, GTV-to-CTV margins of 6 mm can be
utilized (vs. 8 mm in adenocarcinoma), based on a
prior pathologic study showing that this margin can
encompass histologic extension from radiographic
findings in 95 % of tumors.
T2N2M0 adenocarcinoma
of the right upper lobe, with RT lower paratracheal and
subcarinal lymph node involvement
T3N2M0 squamous cell carcinoma of the left upper lobe.
With infiltration of para aortic L.N
PORT
– Postoperative radiation therapy is indicated in the
following circumstances:
• R1 and R2 resections.
• N2 or N3 lymph node positivity.
• Prior studies have also supported the use of PORT in the
following circumstances: close margins, extracapsular
extension, multiple N1 positivity, a high ratio of
positive lymph nodes to resected lymph nodes,
incomplete mediastinal evaluation .
Target Volumes
GTV
• Positive margins or gross disease (R1 and R2 resections)
– The region of positive margins or gross disease, as
discussed with the operating surgeon. Clips may also be
placed in the appropriate region.
– If gross disease is present, we recommend GTV to CTV
margins of 6–8 mm.
Negative margins with N2–N3 positivity (R0 resection)
• Insummary, there is heterogeneity among physicians in
PORT volumes, and possible approaches include:
– Whole mediastinum – Bilateral mediastinum and
ipsilateral bronchial stump; exclude contralateral hilum
and supraclavicular lymph nodes unless involved.
– High-risk nodal volumes – The “one-up, one- down”
technique on the ipsilateral side plus the bronchial
stump. Contralateral lymph nodes are only covered if
involved .
– Involved nodal regions plus the bronchial stump –
Only those nodal stations involved with disease on
imaging or histologically.
• It is important to note that no prospective trials have
compared these treatment volumes with regard to
toxicity and efficacy. Thus, all techniques could be
considered acceptable, though many institutions are
shifting away from whole mediastinal fields and
towards more conformal volumes.
• There is general agreement that the bronchial stump
should be included regardless of treatment volume.
T3N2M0 adenocarcinoma
of the left upper lobe , who underwent induction chemotherapy
and lobectomy with mediastinal nodal dissection. Pathology
demonstrated 2/3 para-aortic lymph nodes involved with disease
RTOG 1106 Required OARs
Structure
Description
Structure definition and contouring instructions
Lung
Lungs –
PreGTV
(composite
of CT1GTV
and PETMTV)
Both lungs should be contoured using pulmonary windows. The right and left lungs can be
contoured separately, but they should be considered as one structure for lung dosimetry.
All inflated and collapsed, fibrotic and emphysematic lungs should be contoured, small
vessels extending beyond the hilar regions should be included; however, pre GTV, hilars
and trachea/main bronchus should not be included in this structure.
Heart
Heart &
Pericardium
The heart will be contoured along with the pericardial sac. The superior aspect (or base)
will begin at the level of the inferior aspect of the pulmonary artery passing the midline
and extend inferiorly to the apex of the heart.
Esophagus
The esophagus should be contoured from the beginning at the level just below the cricoid
to its entrance to the stomach at GE junction. The esophagus will be contoured using
mediastinal window/level on CT to correspond to the mucosal, submucosa, and all
muscular layers out to the fatty adventitia.
Spinal Canal
The spinal cord will be contoured based on the bony limits of the spinal canal. The spinal cord
should be contoured starting at the level just below cricoid (base of skull for apex tumors) and
continuing on every CT slice to the bottom of L2. Neuroformanines should not be included.
Brachial
Plexus
This is only required for patients with tumors of upper lobes. Only the ipsilateral
brachialplex is required. This will include the spinal nerves exiting the neuroforamine from
top of C5 to top of T2. In contrast to prior RTOG lung studies of contouring the major
trunks of the brachial plexus with inclusion of subclavian and axillary vessels, this trial
requests contouring the nerves according to the CT anatomy on every other CT slice. The
structure should extend at least 3 cm above the PTV.
Esophagus
Spinalcord
Brachialplex
RTOG 1106 Optional OARs
Structure
Description
Pericard
Pericardium
Greatves
Aorta
SVC
Great vessels
Aorta
Superior vena
cava
Inferior vena cava
pulmonary vein
pulmonary artery
IVC
PV
PA
Pbtree
CW2cm
Proximal
Bronchial Tree
Chest wall 2 cm
outside of lung
Structure definition and contouring instructions
The structure of pericardium includes pericardial fatty tissue,
part of great vessels, normal recesses, pericardial effusion
(if applicable) and heart chambers. Pericardium starts at one slice above the top of
aortic arch, ends at the last slice of heart apex at diaphragm. Pericardium includes
the heart.
The great vessels should be contoured separately from the heart, using mediastinal
windowing to correspond to the vascular wall and all muscular layers out to the fatty
adventitia (5 mm from the contrast enhanced vascular wall). The great vessel should
be contoured starting at least 3 cm above the superior extent of the PTV and
continuing on every CT slice to at least 3 cm below the inferior extent of the PTV.
For right sided tumors, SVC will be contoured, and for left sided tumors, the aorta
will be contoured. The ipsilateral PA will be delineated for tumor of either side.
This structure includes the distal 2 cm of the trachea, the carina, the right and left
mainstem bronchi, the right and left upper lobe bronchi, the intermedius bronchus,
the right middle lobe bronchus, the lingular bronchus, and the right and left lower
lobe bronchi.
Chest wall can be autosegmented from the ipsilateral lung with a 2-cm expansion in
the lateral, anterior, and posterior directions. Anteriorly and medially, it ends at the
edge of the sternum. Posteriorly and medially, it stops at the edge of the vertebral
body with inclusion of the spinal nerve root exit site. CW2cm which include
intercostal muscles, nerves exclude vertebrate bodies, sternum and skin. This can be
accomplished through auto-expansion of the ipsilateral lung (within 3 cm range of
PTV).
Locating the Brachial Plexus
Timmerman’s Trick-1
clavicle
1st rib
• Vein, artery, and nerve (VAN,
anterior to posterior) will go over
the 1st rib and under the clavicle
• Using coronal images, find the
plane where vascular/nerve
structures (tubes and wires) pass
between the 1st rib and clavicle
• Roughly contour these neurovascular tissues in this coronal
plane (as shown in yellow)
• You will use these rough contours
in the next step
Locating the Brachial Plexus
Timmerman’s Trick-1
N A
V
• Project coronal contours onto axial
images (yellow points shown on
axial image)
• In the region between the projected
points, identify the VAN on either
side. Contour the “N” as the root(s)
of the brachial plexus
• Note: Finding the brachial plexus
on the uninvolved side will help in
finding it on the involved side
• Note: IV contrast greatly facilitates
this task (see contrast in artery)
Proximal Bronchial Tree
• The proximal bronchial tree can be contoured using
mediastinal windows on the CT scan to correspond to the
mucosal, submucosa, and cartilage rings and airway
channels associated with these structures. It can be
contoured as one structure, including the most inferior 2 cm
of distal trachea and the proximal airways of both sides.
Recommendation based on Timmerman et al for RTOG 0236 and RTOG 0618,
Bezjak et al for RTOG 0813
PBT starts at 2 cm above
carina
Proximal Bronchus Tree continues…
Proximal Bronchus Tree Ends
at the level of lobar bronchus bifurcating
into segmental bronchus
• Chest wall can be autosegmented from the ipsilateral
lung with a 2-cm expansion in the lateral, anterior,
and posterior directions. Anteriorly and medially, it
ends at the edge of the sternum. Posteriorly and
medially, it stops at the edge of the vertebral body .
Chest Wall (CW)
CW refers to CW2cm which include intercostal muscles, nerves
exclude vertebral bodies, sternum and skin. This can be
accomplished through auto-expansion of the ipsilateral lung
(within 3 cm range of PTV).
Chest wall
CW contouring starts at 3 cm above the PTV
Chest Wall
CW refers to CW2cm which include intercostal muscles, nerves
exclude vertebral bodies, sternum and skin.
The inferior end of PTV
3 cm below PTV
CW ends at 3cm from the inferior edge of PTV.