ESTRO 36 Abstract Book

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S586 ESTRO 36 2017
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Many patients receiving fractionated radiotherapy (RT) for
head-and-neck cancer have marked anatomic changes
during their course of treatment. We conducted a study to
quantify the magnitude of these anatomic changes with
systematic CT re-scans done after 1st week and 4th week
of treatment.
Material and Methods
A total of 30 patients with head and neck cancer treated
with Intensity modulated radiotherapy are enrolled in the
study. All patients underwent re-scans after 1st week and
4th week of radiation. Volumetric changes were analyzed
for Right parotid and Left parotid.
Results
Thirty patients were analyzed. Mean volumes of right
parotid at initial, after 5# and after 20# was 21.62, 17.55
and 14.53 cc. Mean reduction volume after 5# and 20#
was 4.07 and 7.09 cc. Mean volumes of left parotid at
initial, after 5# and after 20# were 22.70, 17.86 and
14.13cc. Mean reduction volume after 5# and 20# is 4.83
and 8.57cc.
Conclusion
Measurable anatomic changes occurred throughout
fractionated external beam RT for head-and neck cancers.
The data may, therefore, be useful in the development of
an adaptive RT strategy that takes into account such
treatment-related anatomic changes. Such a strategy
would maximize the therapeutic ratio of RT
EP-1074 Dose impact using standard head and neck
immobilization system in brain tumours
M. Rincon1, J. Olivera1, J. Penedo1, I. Prieto 1, S. Gomez1,
M. Garcia1, J. Luna1, D. Esteban 1, A. Ilundain1, J. Vara1
1 Fundación Jimenez Díaz, Radiotherapy, MADRID, Spain
Purpose or Objective
To evaluate the dosimetric impact using the standard head
and neck immobilization system during the radiotherapy
course in patients with brain tumours.
Material and Methods
10 cases of glioblastomas patients were analyzed
In our department, the standard immobilization system for
brain tumours consists of a flat carbon fiber headboard,
an acrylic head support and an IMRT reinforced
thermoplastic mask.
CT in 3-mm slice thickness was obtained. The image fusion
of CT/MRI allowed a more correct delineation of the
planning target volume (PTV) and the organs at risk
(brainstem, chiasm, optic nerves and crystalline lens).
Three fiducial marks were placed on the mask: two lateral
marks and one on midline. The isocenter was located in
the center of the three markers.
In all patients two plans were considered: with and
without the inmobilization system contoured.
The treatment planning was performed using Monaco
planning system (version 3.30.01) based on the Monte
Carlo algorithm. Six MV photon beams generated from
Elekta Synergy Beam Modulator linac equipped with 40
pairs of opposing leaves (4mm thickness at isocenter) were
utilized.
A double-arc volumetric modulated arc therapy (VMAT)
technique was used: one arc from 50º to 180º and another
from 180º to 310º, both in the clockwise, avoiding eyes.
The target prescription dose was 60 Gy to tumoral bed.
The maximum dose in organs at risk brainstem and chiasm,
the dose at the isocenter and D95 and Dmean of PTV were
compared. The difference errors were analyzed.
Results
D95 and Dmean with and without the inmobilization
system contoured showed differences of 0.7% and 0.6%
respectively. The maximun dose in brainstem and chiasm
were lower by 0.9% and 0.4%. The dose at the isocenter
decreased by 0.5 %
Conclusion
The dose impact using standard head and neck
immobilization system in brain tumours was not
significant, less than 1 %, even in the worst case where
this accessory directly interfered with the treatment
beam. With other immobilization systems this attenuation
should be measured and implemented into the treatment
planning process to diminish it when it was necessary.
EP-1075 Role of Diffusion Weighted Imaging in
Laryngeal & Hypopharyngeal Cancers treated with
Radiotherapy
S. Pavamani1, S. Thomas1, P. Surya2, R. Michael3, G.
Mathew3, S. Mathews 3, S. Balukrishna1, M. Sunithi 2
1Christian Medical College Hospital, Radiation Oncology,
Vellore, India
2Christian Medical College Hospital, Radiology, Vellore,
India
3Christian Medical College Hospital,
Otorhinolaryngology, Vellore, India
Purpose or Objective
Locally Advanced Squamous Cell Carcinoma of the Larynx
& Hypopharynx can be treated with an Organ Preserving
approach utilising Concurrent Chemoradiotherapy (CRT),
Radical Radiotherapy (RT) or targeted therapy. Due to
various reasons, some patients may not respond to this
treatment & will eventually need salvage surgery.
However, if the outcome of the treatment can be
predicted beforehand, this can prevent unnecessary side
effects & toxicity. The patient can then be offered surgery
upfront. Diffusion Weighted MRI (dWMRI) is an imaging
modality wherein an increase in the Apparent Diffusion
Coefficient (ADC) in the tumour indicates an increase in
the movement of water molecules. This in turn indicates
a decrease in the cellularity in the tumour & tumour
response. Thus, a rising ADC value during treatment versus
Pretreatment ADC values may be used to predict
outcomes.
The aim of this study was to investigate the role of
diffusion weighted MRI derived parameters like ADC, as an
imaging biomarker, to predict response to RT in locally
advanced squamous cell carcinoma of the larynx and
hypopharynx.
Material and Methods
From May 2014 to August 2015, 19 patients with locally
advanced laryngeal & hypopharyngeal malignancies,
treated with organ preservation intent with concurrent
radiotherapy with Cisplatin (n=14), radiotherapy with
Nimotuzumab (n=2) and radical radiotherapy (n=3) were
recruited. The patients were all male with predominantly
T3 stage. They were assessed for treatment response with
dWMRI at baseline, first week, fourth week during RT and
at the time of first response assessment at 6 to 8 weeks
after RT. The ADC values were compared at different time
points and correlated with the treatment response.
Results
All the 19 patients in the study showed an increasing trend
in the ADC values over the chosen 4 different time points.
It was observed that an abrupt rise from the pretreatment
ADC to the first week ADC was characteristic of complete
response while a gradual rise of ADC over the different
points suggested a partial treatment response. The
patients who responded to chemoradiation therapy had a
higher pretreatment ADC than patients with partial
response. At the last follow up, 12 patients were disease
free, while 5 patients developed recurrence. Four patients
with recurrence had shown a partial response while only
one had exhibited a complete response during RT. One
patient died during treatment of aspiration pneumonia
while undergoing CRT & another did not follow up after
completion of treatment.
Conclusion
This study suggests that an abrupt rise in the ADC value in
the tumour after one week of treatment may predict
complete response & long term tumour control. However
this finding needs to be investigated in a larger cohort of