ESTRO 36 Abstract Book

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S51 ESTRO 36 2017
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5. Zegers CM et al. In-vivo quantification of hypoxic and
metabolic status of NSCLC tumors using [18F]HX4 and
[18F]FDG PET/CT imaging. Clin Cancer Res 2014.
20(24):6389-97.
SP-0104 The impact of tumour heterogeneity on
radiation therapy outcomes
M. Gerlinger 1
1 The Institute of Cancer Research and The Royal Marsden
NHS Foundation Trust, Sutton, United Kingdom
Intratumour heterogeneity, characterized by branched
evolution with multiple subclones that evolve
simultaneously, has been identified in most solid tumour
types. Subclones may vary in their therapy sensitivity and
are often spatially segregated. The talk will discuss how
this subclonal heterogeneity complicates effective
targeting and the potential role of combination therapy
approaches and focal therapies as key strategies to
address heterogeneity.
OC-0105 Hybrid F-MISO PET/MRI for radiation therapy
response assessment in cervix cancer
M. Daniel1,2, P. Andrzejewski 1,2, A. Sturdza2, K. M
ajercakova1,2, P. Baltzer1,3, K. Pinker1,2, W. Wadsak 1,4, R.
Pötter1,2, T. Hellbich1,3 , P. Georg1,5, D. Georg 1,2
1 Medical University of Vienna, Christian Doppler
Laboratory for Medical Radiation Research for Radiation
Oncology, Vienna, Austria
2 Medical University of Vienna, Department of Radiation
Oncology, Vienna, Austria
3 Medical University of Vienna, Department of Biomedical
Imaging and Image-guided Therapy, Vienna, Austria
4 Medical University of Vienna, Department of Nuclear
Medicine, Vienna, Austria
5 EBG Med Austron GmBH- Wr. Neustadt, Wr. Neustadt,
Austria
Purpose or Objective To investigate the spatio-temporal
stability of the tumor characteristics in cervix cancer
patients undergoing radiotherapy with advanced imaging
methods. More specifically, repetitive multiparametric
MR-PET imaging prior, during and after the end of chemo-
radiotherapy was performed utilizing a hybrid scanner.
Material and Methods
Six patients with cervical cancer participated in this
prospective study. All patients received chemo-
radiotherapy, with a total IMRT prescription dose of 45Gy
(25x1.8Gy in 5days/week) followed by a MRI guided
brachytherapy boost (4x7Gy). Patients underwent four
PET/MR examinations performed on a Siemens Biograph
mMR PET/MR at baseline (BL), in treatment week 2 (TP1)
and 4 (TP2) of the IMRT schedule, and 3 months after end
of treatment (FU). At all time-points T2w turbo spin echo,
DWI, DCE T1w gradient echo with 35 repetitions and
hypoxia PET scans with 18F-fluoromisonidazole (F-MISO)
were acquired. ADC, Ktrans and iAUC maps were generated
(cf. figure).
All images were registered to neighboring time-points
using RayStation (RaySearchLaboratories, Sweden)
utilizing a hybrid deformable registration algorithm.
Uterus, cervix, a reference structure for tumor to
background ratio (TBR) calculation in gluteal muscle (GM)
were delineated on all images. The GTV was defined on
T2w images for the first 3 examinations. A sphere of 1cm
diameter was created around the hottest voxel in the GTV
of the PET to define the peak value. Datasets were
assessed for tumor volume, enhancement kinetics (K trans,
iAUC), diffusivity (ADC) and F-MISO-avidity (TBR). The TBR
was evaluated for the mean of the peak-sphere and the
top 10% (TBRtop10%) and the mean (TBRmean) of the TBR
values in the whole GTV. Paired t-tests were performed to
evaluate statistical significance.
Results
The mean volume of the GTV decreased from 62±42cm3
(BL) to 50±35cm3 (TP1) and 20±18cm 3 (TP2). The cervix
volume at FU was 24±4cm3. The mean GTV ADCs (in x10-
3mm2/s) were 0.98±0.10 at BL, and significantly increased
during follow up investigations with 1.17±0.15 at TP1,
1.16±0.10 at TP2 and 1.25±0.12 at FU. No significant
changes were found for the TBR peak. However, for the
TBR mean as well as the TBRtop10% the following drop was
observed: from 1.81±0.14 (BL) to 1.52±0.10 (TP2) and
3.24±0.40 (TP1) to 2.40±0.39 (TP2), respectively. Intensity
of T2w images, Ktrans and iAUC showed the same behavior:
an increase at TP1 followed by a drop at TP2 as well as
FU. The following changes reached statistical significance:
T2w: BL-TP1(+20%), BL-TP2(-16%); iAUC: BL-FU(-29%);
Ktrans: BL-FU(-55%), TP1-TP2(-32%).
Conclusion
First hybrid PET/MR results confirm previous results from
serial MR and PET/CT, i.e. increasing ADC, Ktrans and iAUC
in treatment week 2 correlates with morphological
response. High FMISO uptake showed neither local stability
nor persistency throughout the course of treatment. Final
conclusions on quantitative PET/MR imaging for treatment
response in cervix cancer requires a larger patient cohort.
Symposium: Innovations in ion beam therapy
SP-0106 Reducing range uncertainties: new
approaches for stopping power determination and in-
vivo range verification
K. Parodi1
1Ludwig Maximilians Universität München, Department of
Medical Physics, München, Germany
Radiation therapy with protons and heavier ion beams is a
rapidly emerging treatment modality which promises
precise delivery of a biologically effective dose to the
tumour, with optimal sparing of surrounding critical
organs and healthy tissue. To this end, over the last years,
technological advances in beam delivery have been
accompanied by an increasing integration and usage of
imaging in the entire chain of fractionated treatment,
from pre-treatment identification and characterization of
the tumour up to anatomical guidance for patient
positioning at the treatment site.
Despite these recent technological advances, full clinical
exploitation of the favorable ballistic properties of ion
beams is still hampered by the yet unsolved problem of
range uncertainties. To this end, new imaging approaches
are being extensively investigated to tackle this issue at
the stage of treatment planning or treatment delivery. In
this contribution, special emphasis will be given to pre-
treatment transmission imaging of multi-energy X-ray
sources or energetic ion beams for refined assessment of
the tissue stopping properties, as well as online/post-
treatment detection of acoustic and nuclear-based
emissions induced by ion interaction in tissue for in-vivo
verification of the beam range. In particular, the main
ongoing developments and initial pre-clinical or clinical
experience will be critically reviewed, discussing the
prospects of novel imaging methods for reducing range
uncertainties in ion beam therapy.
SP-0107 Mechanisms and Models of Particle Relative
Biological Effectiveness (RBE)
D.J. Carlson1
1Yale University School of Medicine, Therapeutic
Radiology, New Haven- CT, USA