Transcript Conformal Therapy for Lung Cancer

Conformal Therapy
for Lung Cancer
B. Schicker, F.J. Schwab*, U. Götz
Institute of Radiotherapy and Radiation Oncology
St. Vincenz-Krankenhaus Limburg
*Clinic of Radiotherapy
University of Würzburg
Definition
INTRODUCTION
For lung cancer radiotherapy is an essential treatment mode.
The major problem for the treatment planning is the fact that
the target volume is surrounded by organs at risk. Acute or late
reactions of the lung, the myelon and the heart are dose limiting
factors. If curative doses are aspired the old fashioned opposed
fields techniques are not applicable because of the high dose
load to the organs at risk. Curative doses for lung cancer,
however, usually exceed 70 Gy. Therefore conformal treatment
techniques have to be developed aiming at the reduction of the
normal tissue complication probability and the high tumor
control probability.
ADJUVANT TREATMENT
For local advanced tumor stages the postoperative irradiation of
the regional lymphatics and of the bronchial stump is indicated.
The mediastinum should always be included in the clinical
target volume if involved nodes were found but no systematic
lymph node dissection was performed. The supraclavicular
lymph nodes are not included in the CTV for adjuvant
treatment with curative intent. The involvement of these lymph
nodes probably improves local control, whereas the
improvement of survival remains questionable. The lymph
nodes included in the CTV are: the intrapulmonary, the
subcarinal, the tracheobronchial, the paratracheal and the
preaortic group. For lower lobe primaries the inclusion of the
lymph nodes along the ligamentum pulmonale and the
paraesophageal nodes should be considered.
Radiotherapy
decades ago
Conventional Opposed Fields Technique
based on radiographs
Conventional Opposed Fields Technique
Change from Radiograph to Target Volume
Traditional irradiation portals
recommended in textbooks for
irradiation of lung cancer
patients.
selected clinical target volume
based on the oncological principles (no inclusion of the
supraclavicular and contralateral hilar lymph nodes in
the CTV for curative RT).
Development of Conformal Treatment
Techniques


first step: precise definiton of the
planning target volume based on
oncological criteria
conformal treatment = precise
irradiation of a precisely defined PTV
Target Volume
for adjuvant treatment
Z +8
Z +3
Z +0
Z -2
Z -4
Z -8
Definition
CONFORMAL RADIOTHRAPY
A high dose to the PTV means a high tumour control
probability were as a low dose to the normal tissue or organ at
risk means a low normal tissue complication probability
Low side effects = live quality for the Patient
BENEFIT FOR PATIENT
Ideal Treatment vs. Reality
Dose Distribution
Ideal:
Real:
D(PTV) = 100%
D(PTV) ~ 100%
D(NT,OAR) = 0%
D(NT,OAR) >> 0%
Ideal Treatment vs. Reality
Dose Volume Histogram
Volume [%]
Volume [%]
100
100
Normal Tissue,
Organ at Risk
PTV
100
Dose [%]
100
Dose [%]
Aim of the Optimization
- minimum requirements -



High TCP and low NTCP:
high dose within the PTV and a good protection of the
OAR
Reduction of the dose to the OAR below critical values
(tolerance doses)
Concentration of the therapeutic dose on the PTV:
Dose homogeneity within the PTV
(ICRU recommendations -5 % ... +7 %)
Development of a 3-D Conformal Standard
Technique for Lung Cancer

From opposed fields to conformal technique
=>
???
Definition
3 Dimensional Conformal
- CT based Treatment planning
- Slice distance 1.0 or 0.5 cm
- Definition and delineation of PTV and Organ at risk in every
slice
- using other imaging procedures as MR, PET etc.
-Calculation and optimisation of the dose distribution in every CT
slice to achieve a homogenous dose distribution
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a
Standard Technique for
Lung Cancer
PTV
Lung
Heart
Myelon
Development of a Standard Technique
Standard Beam Set up
- Isocenter – placed at the ventral tip of the vertebral body
- easy to find uneder X-Ray controll from 0° and also 90° gantry angle
Development of a Standard Technique
Standard Beam Set up
Aim of Field 1 is to spare a maximum volume of both lungs
F1
0°
Development of a Standard Technique
Standard Beam Set up
The gantry angle and blocking of field 2 (135°) was chosen to protect
the myelon
F2
135°
Development of a Standard Technique
Standard Beam Set up
Field 3 (40°) reduce the high dose regions in the left lung and contribute
to a better adaptation of the isodoses to the PTV
Standard Technique
at the ISRO Limburg

3 fields:

myelon)
start with dose contribution 1 : 1 : 1
field shaping using beams eye view


0° fixed wedge (lung)
~ 140° fixed wedge (myelon)
40° ... 80° fixed or arc, wedge ?
(heart, contralateral lung,
good protection of the contra-lateral lung
myelon dose (adjustable from 30% to 70%)
below critical values for curative total doses
Clinical Case 1
Adjuvant Treatment
The 72 year old patient with a non small cell left
localized lung cancer was operated. The primary
lung cancer infiltrated the left pulmonary artery.
A questionable R0 resection was performed. An
adjuvant radiotherapy was indicated. From 12
examined lymph nodes 5 were found involved. A
total dose of 66.6 Gy was applied in this clinical
case. For the main series the target volume was
treated with a dose of 50.4 Gy and for the boost
technique a dose of 16.2 Gy was given. For both
series a dose per fraction of 1.8 Gy was chosen.
ZV
+4 cm
ZV
-1 cm
ZV
-3 cm
Clinical Case 1
Clinical Case 1
Field 3 (35°) and
4 (100°) reduce
the high dose
regions in the left
lung and
contribute a
better adaption of
the isodoses to
the PTV.
Clinical Case 1
Full
homogeneity
over all slices
requires two
further fields (5
and 6).
Conformal Therapy
for Lung Cancer
First International
Symposium on
Target Volume
Definition
F.Schwab
Technique for Case 1
Variation of the Standard Technique
HS
+6 cm
95%
85%
70%
50%
Clinical Case 1
95%
85%
70%
50%
HS
+4 cm
HS
0 cm
95%
85%
70%
50%
Clinical Case 1
95%
85%
70%
50%
HS
-1 cm
Clinical Case 1
95%
85%
70%
50%
HS
-3 cm
HS
- 4 cm
95%
85%
70%
50%
Clinical Case 1
frontal / sagittal dose distribution
100%
95%
90%
85%
80%
70%
50%
30%
10%
frontal
sagittal
Clinical Case 1
DVH
PTV
Lung
Myelon
Clinical Case 1
DVH Box / 3 Field Technique
PTV
Lung
Myelon
Clinical Case 1
Boost
Clinical Case 1
Boost – Beam Setup
BST
-1 cm
95%
85%
70%
50%
Clinical Case 2
Radiotherapy after Pneumonectomy
A 46 year old male patient with a left located non
small cell lung cancer of the upper lobe with
infiltration of the upper lung vein. Nine involved
nodes from 29 examined nodes were described. In
many of the examined lymph nodes a capsule
disruption was found. The CTV includes the
paratracheal area, the upper mediastinum, the aortic
pulmonary window, the left hilus and the subcarinal
area. The lymph node capsule disruption and the
infiltration of the upper pulmonary vein determine
the necessity of a high total dose (at least 66 Gy).
Clinical Case 2
Clinical Case 2
+ 8 cm
100%
95%
90%
85%
80%
70%
50%
30%
10%
Clinical Case 2
+6 cm
100%
95%
90%
85%
80%
70%
50%
30%
10%
Clinical Case 2
- 2 cm
100%
95%
90%
85%
80%
70%
50%
30%
10%
Clinical Case 2
100%
95%
PTV
90%
85%
Myelon
Lung
80%
70%
50%
30%
10%
Clinical Case 3
Definitive radiotherapy
A primary inoperable periphery non-small cell lung
cancer of the right upper lobe was diagnosed for the
77 year old female patient. In this case the CTV
included only the tumor with small margins as
shown in figure 23A and B. A total dose of 68.4 Gy
was applied.
Clinical Case 3
Clinical Case 3
95%
85%
70%
50%
Clinical Case 3
95%
85%
70%
50%
Evaluation of the Treatment Plans

do the isodoses only look nice or
can the patient profit from the conformal technique?

=> analysis of the DVHs

Treatment Index TI
TI := QI(PTV)/(Dmax(m)*QI(m)+Dmean(l)*QI(l)+Dmean(h)*QI(h))
m = myelon
l = lung (left and right)
h = heart / myocard
side condition: no violation of critical doses
Evaluation of the Treatment Plans
Treatment Index
Treatment Index TI
3,50
3,09
3,00
3,00
2,65
TI in a.u.
2,50
1,90
2,00
1,56
1,40
1,50
1,00
0,50
se
ca
6F
nd
ar
1
d
3F
St
ar
F
ox
-4
70
B
St
a
F
O
pp
O
pp
F
(9
0
(a
p-
+2
pa
)
)
0,00
Technique
TI=QI(PTV)/(Dmax(m)*QI(m)+Dmean(l)*QI(l)+Dmean(h)*QI(h))
Conclusions and Discussion
The prerequisite for a conformal therapy is a
precisely defined target volume in a 3D patient
model. The target volume has to be defined on
the basis of oncological criteria and the success
of the therapy has to be checked in clinical
studies. The clinical target volumes presented
here for the adjuvant and definitive
radiotherapy are different from that nowadays
usually shown in the clinical textbooks.
Conclusions and Discussion
One of the advantages of conformal treatment
planning is the reduction of the dose load to the
normal tissue and to the organs at risk compared to an
opposite field technique. The dose at the organs at risk
is lowered in two ways: First the total dose is reduced
on the basis of the conformal treatment and second the
dose per fraction is reduced resulting in a lowering of
the biological effective dose at the organs at risk. Both
effects in combination allow the application of
curative doses to the target volume. The conformal
techniques, however, also require an improvement in
patient positioning. Finally, modern techniques like
intensity modulated therapy may in future help to
improve the homogeneity of the dose distribution.
Conclusion and Future



conformal therapy => improvement of the treatment
quality
conformal therapy => reduction of the high dose
region for the OARs (responsible for side-effects)
lowering of the daily dose to the OAR additionally
reduces the biological effective dose

IMRT for enhanced dose homogeneity

optimized depth doses
(proton facilities)