ESTRO 36 Abstract Book

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S661 ESTRO 36
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differences existed between the AHF and CF groups in
gender, age, clinical stage or histology. A total of 40
patients (78%) had experienced lymph node metastasis
before treatment. Patients received radiotherapy using
AHF in 17 cases and CF in 34 cases. All patients underwent
thoracotomy after induction CRT. The median duration
between the last day of radiotherapy and the day of
operation was 35 days (range, 16–70). The pathologic
complete response (pCR) rates in the primary tumor and
dissected lymph nodes are shown in Table 1. The pCR rates
of adenocarcinoma after induction CRT in the AHF and CF
groups were 41% (7/17) and 24% (8/34) in the primary
tumor and 50% (8/16) and 50% (12/24) in the dissected
lymph nodes, respectively. The pCR rates of SqCC after
CRT in the AHF and CF groups were 75% (6/8) and 29%
(4/14) in the primary tumor and 63% (5/8) and 64% (7/11)
in dissected lymph nodes, respectively. The SqCC in the
primary tumor had significantly higher pCR rates under
AHF compared to CF (p = 0.02). However, the pCR rates of
adenocarcinoma after CRT in the AHF and CF groups were
similar in both the primary tumor and dissected lymph
nodes.
Conclusion
Chemoradiotherapy using AHF may achieve a higher
pathological therapeutic effect than chemoradiotherapy
using CF for squamous cell lung cancer in primary tumors.
EP-1225 Atlas-based segmentation reduces inter-
observer variation and delineation time for OAR in
NSCLC
W. Van Elmpt1, J. Van der Stoep1, J. Van Soest1, T.
Lustberg1, M. Gooding2 , A. Dekker1
1 MAASTRO Clinic, Department of Radiation Oncology,
Maastricht, The Netherlands
2 Mirada Medical Ltd, Science and Medical Technology,
Oxford, United Kingdom
Purpose or Objective
Tumor and organs-at-risk (OAR) delineations are
considered a major uncertainty in radiotherapy.
Automatic segmentation methods are currently available
that may guide the delineations of OAR. However, the
inter-observer variability in OAR delineations are rarely
studied and the effect of automated methods on
delineation variability has not yet been performed. In this
study we systematically quantified the (reduction of)
inter-observer variation by providing the delineation
expert with an atlas-based generated automatic contour
including time spent on delineations.
Material and Methods
Atlas-based automatic delineations were performed using
commercial available software with an atlas derived for
10 stage I NSCLC patients using institutional delineation
guidelines with minimal anatomical distortions. In a next
step, 20 consecutive prospective stage I-III NSCLC patients
were selected from clinical routine. For these patients, 3
experienced radiation technologists independently
created delineations for heart, mediastinum, spinal cord,
esophagus and brachial plexus according to the
institutional standards. Time taken was also recorded.
Next, the automatic atlas-based contour was provided as
a starting point for a second round of delineations (blinded
for the initial contour). The proposed contour was allowed
to be adapted (or discarded) and modified into a clinical
acceptable contour. The inter-observer variation was
quantified as the non-overlapping volume of the 3
observers for both the initial contours and the adapted
contours. Results are expressed as mean±SD, p-values
calculated using a Wilcoxon test.
Results
Comparing the initial contours with the proposed atlas-
generated contour, the inter-observer variation volumes
reduced significantly for the mediastinum: 253±93 cm3 to
168±103 cm3 (p<0.01), spinal cord: 32±10 cm3 to 17±3 cm3
(p<0.01) and heart: 211±69cm 3 to 136±72 cm3 (p<0.01).
For the esophagus there was no reduction inter-observer
variation volume (p=0.601), also no clinically significant
differences for brachial plexus were observed: 12.9±5.4
cm3 vs 12.2±5.1cm3. The average delineation time for the
above structures was reduced from 18.1±4.8 to 13.2±5.5
minutes (p<0.01), mainly dominated by the reduction in
time needed for the mediastinal delineation and heart.
Conclusion
Besides a reduction in contouring time, the inter-observer
variation is also reduced if an atlas-based segmentation
approach is used as the initial starting point for
delineations. Especially for the larger structures such as
the heart and mediastinum the impact on time gain and
increase of quality is significant.
EP-1226 Stereotactic robotic body radiotherapy for
patients with pulmonary oligometastases
P. Berkovic1, A. Gulyban1, L. Swenen1, D. Dechambre1, P.
Viet Nguyen1, N. Jansen1, C. Mievis1, N. Bartelemy1, P.
Lovinfosse 1, M. Baré 1, F. Lakosi 2, L. Janvary3, P.A.
Coucke1
1C.H.U. - Sart Tilman, Radiotherapy department, Liège,
Belgium
2Health Science Center- University of Kaposvar,
Radiation Oncology, Kaposvar, Hungary
3University of Debrecen - Medical Center, Onco
logy Clinic, Debrecen, Hungary
Purpose or Objective
To analyse local control (LC), pulmonary and distant
progression free survival (pulmonary PFS, DFS), overall
survival (OS) and toxicity in a cohort of patients treated
by stereotactic body radiotherapy (SBRT) for
oligometastatic pulmonary lesions. To evaluate the
potential influence of age, histology, controlled primary,
performance status, biological effective dose (BED) and
other parameters on the obtained results.
Material and Methods
Consecutive patients with up to 3 synchronous lung
metastases were included in this study for Cyberknife at
the Liege University Hospital. All patients were referred
for stereotactic treatment after a full staging including
baseline registration of the pulmonary function, chest and
abdominal diagnostic computed tomography (CT) and
[18F]-fluorodeoxyglucose (FDG) positron emission
tomography (PET)-CT imaging confirming the presence or
absence of tumoral activity at the primary tumour site and
extra-pulmonary metastases. The intended prescription
dose was 60 Gy in 3 fractions, prescribed on the 80%
isodose line and adapted based on clinical risk-factors.
Local control (LC), lung and distant progression free
survival (lung and distant PFS) and overall survival (OS) of
patients were generated using Kaplan-Meier survival
curves. Age, gender, performance status (PS), primary
histology, controlled primary as patient specific, while