ESTRO 36 Abstract Book

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S637 ESTRO 36 2017
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NSM (85.0% and 81.0%, respectively). They considered
age, lymph node involvement, tumor size, extracapsular
extension, involved surgical margins, lymphovascular
invasion, triple negative receptor status and multicentric
tumor as major risk factors. Considering tumor size, lymph
node involvement and age as recurrence risk factors, the
most-often suggested cut-off thresholds of those features
were 5 cm, > 3 lymph nodes and 40 years old, respectively.
Considering that after SSM and NSM, residual breast tissue
can be left behind, the residual tissue considered as
acceptable in the context of an oncologic surgery were 1
to 5 mm and 6 to 10 mm for 55% and 21% of the responders,
respectively. There is no consensus for the necessity of
evaluating residual breast tissue through breast imaging.
Conclusion
Although the indications of post-
operative radiation therapy after SSM and NSM are not well
defined, all standard relapse risk factors were considered
as important, by surgeons, with regards to referring for
post-operative radiation therapy.
EP-1186 Real-time intrafraction motion in breast
radiotherapy using an optical surface scanner
D. Reitz 1, S. Schönecker1, P. Freislederer 1, M. Pazos 1, M.
Niyazi 1, U. Ganswindt1, C. Belka 1, S. Corradini1
1 LMU University of Munich, Radiation Oncology, Munich,
Germany
Purpose or Objective
Intrafraction motion is of special interest in modern breast
cancer radiotherapy. Respiratory motion during intensity-
modulated radiotherapy (IMRT) can cause problems in
inadequate planning target margins or IMRT delivery. To
date, only few data exist on real-time measured
intrafraction motion in breast cancer patients. Continuous
surface imaging using visible light offers the possibility to
monitor patients’ movements in 3D-space without any
additional radiation exposure.
Material and Methods
We observed thirty-one patients during 629 fractions that
underwent postoperative radiotherapy following breast
conserving surgery or mastectomy. During each treatment
session the motion of the patient was continuously
measured using the Catalyst TM optical surface scanner (C-
RAD AB, Sweden) and compared to a reference scan taken
at the beginning of each session. The Catalyst TM system
works through an optical surface scanning with LED light
(blue: λ = 450 nm) and reprojection captured by a CCD
camera (green: λ = 528 nm; red: λ = 624 nm), which
provide target position control during treatment delivery.
For 3D surface reconstruction, the system uses a non-rigid
body algorithm to calculate the distance between the
surface and the isocenter and using the principle of optical
triangulation. Three-dimensional deviations and relative
position differences during the whole treatment fraction
were calculated by the system and analyzed statistically.
Results
Overall, the magnitude of the deviation vector showed a
mean change of 1.3 mm +/- 0.4 mm (standard deviation)
and a median change of 1.1 mm during dose application
(beam-on time only). Along the lateral and longitudinal
axis changes were quite similar (0.9 mm +/- 0.3 mm vs.
0.9 mm +/- 0.5 mm), on the vertical axis the mean change
was 1.1 mm +/- 0.3 mm. The mean net beam-on time of
radiation therapy was 2.8 minutes. There was no linear
correlation between the length of the fraction and the
magnitude of deviation. Pearson’s correlation coefficient
between mean time and mean magnitude of deviation
vector over all patients was 0.25 (p-value= 0.175).
Conclusion
Mean real-time intrafraction motion was within two
millimeters in all directions and is therefore of minor
clinical relevance in postoperative radiotherapy of breast
cancer.
EP-1187 Heart dose evaluation in two free-breathing
and deep-breathing modes of breast cancer patients
R. Anbiae1, A.R. Taji1, A. Ahmari1, Z. Siavashpour2, M.
Beigi1
1Shahid Beheshti Medical University, Radiation Oncology,
Tehran, Iran Islamic Republic of
2Shahid Beheshti University, Medical Radiation
Engineering, Tehran, Iran Islamic Republic of
Purpose or Objective
To investigate how much respiratory manner of breast
cancer patients during external beam radiotherapy would
affect their heart dose.
Material and Methods
21 patients with left breast cancer underwent CT
simulation without contrast in one day and two positions;
breath hold and free breathing, prospectively. Two CT
image sets were imported to treatment planning system
(Eclipse, version 6). Volumes of PTV (that included breast
and chest wall), heart and ipsilateral lung in both image
sets were contoured by an individual radiation oncologist.
An experienced physicist designed the plans for both CTs.
Prescribed dose was 50 Gy in 25 fractions for all included
cases. Plans were then confirmed by the oncologist and
heart and lung dose volume parameters were
exported. Lung and heart Volumes, their V30 and V22.5
and also mean heart dose (MHD) in two condition were
studied and analyzed.
Results
Mean age of patients was 46.9±12.1.Twelve patients had
done MRM and 9 of them had done BCS. Mean heart
volume, its V30, V22.5 and MHD in two breathing
conditions, breath hold and free breathing, were 519±108
and 526±107 (P=0.545), 1.89±2.41 and 62.88±2.04
(P=0.030) , 2.41±2.68 and 4.35±3.42 (P=0.048) and
0.98±0.7 and 1.42±0.5 (P=0.002), respectively. Also left
lung volume and V30 of lung in breath hold and free
breathing modes were 1763±315 and 1114±219 (P<0.001)
and 8.72±3.27 and 8.92±4.29 (P=0.819) respectively.
Person correlation did not show linear relation between
lung volume and its mentioned DVH parameters; for MHD
obtained r=-0.421 (P=0.057), for heart V30 and V22.5
obtained r=-0.500 (P=0.021) and obtained r=-0.371
(P=0.097) and also, for heart volume r=0.032 (P=0.889).
Conclusion
All MHD and heart V30 and V22.5 variables were
significantly higher with deep breathing in our study. It
was shown that irritated heart volume was reduced
significantly in this condition. V30 of lung were lower in
deep breathing so deep breathing can be efficient method
in left breath teletherapy.
EP-1188 DIBH radiotherapy in left-sided breast cancer
patients using an optical surface scanning system
S. Schönecker 1, M. Pazos 1, P. Freislederer 1, D. Reitz1, H.
Scheithauer1, S. Corradini1, C. Belka 1
1LMU University of Munich, Radiation Oncology, Munich,
Germany
Purpose or Objective
There is a potential for adverse cardiovascular effects in
long-term breast cancer survivors following adjuvant
radiotherapy (RT). For this purpose, the deep inspiration
breath-hold technique (DIBH) has been introduced into
clinical practice, to maximally reduce the radiation dose
to the heart. In the present study radiotherapy in DIBH was
applied using the optical surface scanning system
CatalystTM/SentinelTM.
Material and Methods
A total of 38 patients with left-sided breast cancer
following breast conserving surgery were analysed.
Normofractionated and hypofractionated radiotherapy
protocols were eligible for this prospective clinical trial.
Patient surface data and respiratory parameters were
acquired using the laser surface scanner SentinelTM (C-RAD