ESTRO 36 Abstract Book

780 / 1096

S764 ESTRO 36
_______________________________________________________________________________________________
with cervical cancer (CC) were treated with radical
radiochemotherapy. 17 pts with CC were treated
palliative with radiotherapy, 10 pts with hepatic lesions
(1 HCC and 9 meta ad hepar) treated with chemotherapy,
7 pts with pancreatic ca treated with chemotherapy, 2
breast ca treated with chemotherapy ( 1 with RT and 1
with CT), 11pts with lung ca treated with chemotherapy ,
7 pts with rectal ca. treated with radiotherapy, 4 pts with
ca. of sigmoid colon treated with chemotherapy, 2 pts
with gastric ca. treated with chemotherapy and 1 with
radiotherapy. The Celsius TCS hyperthermia system, an
electro-hyperthermia, with a maximum output of up to
500 Watts was used. Two different electrode sizes were
applied externally by physical means to the region with
tumour in a targeted and controlled manner. The aim was
to increase the temperature to 41 oC - 42oC, one session
lasted 60min. It was combined with either chemotherapy
or radiotherapy twice per week. Toxicity of the skin was
evaluated at every session with RTOG/EORTC
classification system. The tolerance of treatment was
ranged as Group 1: very good if there were 1-2 pauses
because of discomfort with no other symptoms, Group 2:
good- 3-4 pauses because of discomfort and skin toxicity
Grade 1, Group 3: poor- > 4 pauses or shortening of
hyperthermia course because of itching and skin
toxicity>=Gr 2.
Results
Local deep hyperthermia was easily tolerated. 78 pts
didn’t report any problems and were assigned to Group 1.
16 pts were assigned to Group 2 and only 2 pts to the group
“poor”. Toxicity was generally mild and never of grade 3.
1/10 pts felt pain in the last few minutes of the session.
Acute radiation toxicity was the same with or without
hyperthermia. There was a reduced tolerance of
hyperthermia in obese persons, with folds of skin on the
abdomen. This is primarily due to the fact that between
folds of skin sweat is collected what increases negative
impression from temperature. All patients with tumours
located in pelvis, reported pressure on the coccyx. We
haven’t observed any increased vaginal bleeding during
radical and palliative treatment of CC.
Conclusion
Tolerance associated with hyperthermia was very good
and most patients felt comfortable during this treatment.
Acute toxicity of the skin during the treatment was low.
EP-1432 Advantage of butterfly-vmat versus vmat in
mediastinal tumors
J. Luna1, A. Ilundain1, S. Gómez-Tejedor1, D. Esteban1,
M. Rincón1, J. Olivera1, W. Vásquez1, I. Prieto1, L.
Guzmán 1, J. Vara1
1 Fundación Jiménez Díaz, Radiation Oncology, Madrid,
Spain
Purpose or Objective
There is a growing concern about the risks of late adverse
effects in young people who receive mediastinal
radiotherapy. The amazing technical advance has
achieved better planned treatments. At present, the new
focus of interest is to minimize the low doses in organs at
risks (OARs)
Material and Methods
We present our first results of a new protocol in our
Department for mediastinal radiotherapy. This protocol
includes the comparison of two treatment plannings for
every patient: volumetric modulated arc therapy (VMAT),
and Butterfly VMAT (a technique developed by the
University of Turin, Radiation Oncology Unit). VMAT was
performed with a double arc of 360º. B-VMAT consisted of
2 coplanar arcs of 60º (gantry starting angles 150º and
330º) and 1 no-coplanar arc of 60º (gantry starting angles
330º, couch angle 90º).
Until now, five patients have been included: Three
mediastinal lymphomas in young women (total dose 36 Gy
in two cases and 30 Gy in the other one), one patient
diagnosed of hemangiopericytoma located at internal
mammary chain (total dose 50 Gy) and the fifth patient
diagnosed of thymoma (54 Gy)
In the dose- volume histogram, regarding the PTV, the
parameters analyzed were V95, V98, V107, Medium dose,
Homogeneity index (HI) and conformity index (CI). For
OARS- (heart, lung and breast) and body, several
dosimetric parameters were registered.
Results
Our results show similar data in PTV coverage, IH and CI.
Regarding the OARs, dosimetric parameters were
equivalent in lung, heart and body. However, breast doses
were clearly lower with B-VMAT, mainly the lowest doses
(V4 and V10). For V4 , the medium value was 45.6% (7.8%
– 63.1%) for VMAT and 21.5 % (0.7%- 60.1%) for B-VMAT.
For V10, the VMAT medium value was 23.2% (0%-
37.2%) and the B-VMAT medium value was 8.9% (0%-
24.4%).
Conclusion
B-VMAT for mediastinal tumors is clearly superior to usual
VMAT for breast doses, mainly the low doses, and
equivalent in the rest of dosimetric parameters. Although
the inclusion of more patients is needed, our preliminary
results show B-VMAT like a great technical advance in
mediastinal radiotherapy.
Electronic Poster: Physics track: Basic dosimetry and
phantom and detector development
EP-1433 Photoneutron Flux Measurement via NAA in a
Radiotherapy Bunker with an 18 MV Linear Accelerator
T. Gulumser1, Y. Ceçen1, A.H. Yeşil1
1Akdeniz University- School of Medicine, Department of
Radiation Oncology, Antalya, Turkey
Purpose or Objective
In cancer treatment, high energy X-rays are used which
are produced by linear accelerators (LINACs). If the energy
of these beams is over 8 MeV, photonuclear reactions
occur between the bremsstrahlung photons and the
metallic parts of the LINAC. As a result of these
interactions, neutrons are also produced as secondary
radiation products (γ,n) which are called photoneutrons.
The study aims to map the photoneutron flux distribution
within the LINAC bunker via neutron activation analysis
(NAA) using indium-cadmium foils.
Material and Methods
The radiotherapy bunker hosts a Philips SLI-25 LINAC which
is used for experimental studies. The measurements are
taken at the highest energy of the LINAC which
corresponds to 18 MeV bremsstrahlung photons. Indium
and cadmium foils were used at 91 different points within
the bunker. Neutron activation was performed by
irradiating the room with 10000 monitor units (MU) at
different gantry angles. The field was 40x40 cm 2 open. The
activated indium foils are then counted in a High Purity
Germanium (HPGe) detector system.
Since indium has a high absorption cross section for
thermal and epithermal neutrons, bare indium foil
irradiation results in flux information of that region.
However cadmium has high absorption cross section in the
epithermal and fast region. If one filters the indium foils
by cadmium coatings, the difference in the count yields
thermal fluxes which are of interest for the doses to the
patients in radiotherapy.
Results
Result of the analysis shows that the maximum neutron
flux in the room occurs at just above of the LINAC head
towards to gun direciton. This is expected since most of