ESTRO 36 Abstract Book

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S534 ESTRO 36 2017
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Results
Among the 14 cell lines analyzed, strong differences in
clonogenic survival were observed. Using the linear-
quadratic model, very high goodness-of-fit levels were
obtained (R 2≥0.98). However, obvious differences in
radiosensitivity between several cell lines were not
revealed by the respective α/β values which failed to
reflect the overall steepness of survival curves.
Data reduction by PCA allowed the extraction of
radioresistance scores. Notably, more than 70% of the
variance in the dataset was covered by the first PC.
Correlation of radioresistance scores with mRNA
expression levels of DDR regulators identified potential
predictors of radioresistance. Target validation using RNA
interference and selection of suitable pharmacological
inhibitors are ongoing.
Conclusion
Dimensionality reduction by PCA is a suitable method to
extract scores of radioresistance from clonogenic survival
datasets which can be correlated with other types of data,
such as mRNA expression levels. This approach facilitates
the identification of DDR regulators which may be further
validated as potential biomarkers of radioresistance
and/or targets for radiosensitization.
PO-0974 Biomarkers of radiosensitivity for patient
stratification and personalized radiotherapy treatment
E. Palumbo1, C. Piotto1, L. Baggio 1, E. Groff1, E. Calura2,
F. Busato1, B. El Khouzai1, E. Fasanaro1, M. Rigo1, L.
Loreggian1, C. Romualdi2, A. Russo3, M. Mognato2, D.
Zafiropoulos4, L. Corti1
1 Istituto Oncologico Veneto IOV-IRCCS, UOC of
Radiotherapy, Padua, Italy
2 University of Padua, Department of Biology, Padova,
Italy
3 University of Padua, Department of Molecular Medicine,
Padova, Italy
4 National Laboratories of Legnaro- Italian Institute of
Nuclear Physics, LNL-INFN, Padua, Italy
Purpose or Objective
The personalization of radiotherapy (RT) represents the
goal of future clinical radiation trials. A screening tool
able to classify each patient according to his/her own
sensitivity to ionizing radiation (IR) before the
administration of RT would be essential to set
personalized dosing schedules, effective in improving RT
outcomes and in reducing side effects. Genetic variation
is a likely source for the normal tissue radiosensitivity
variation observed among individuals. Mutations in key
genes of the DNA-Damage Response (DDR) pathway, or the
individual modulation of DDR gene expression after IR-
exposure, may underlie these differences. This study aims
at defining a genetic signature useful to discriminate
patients undergoing RT as radiosensitive, normal and
radioresistant and to predict the likelihood of a late IR-
toxicity. In this frame, gene expression data concerning
DDR pathway, obtained from blood samples of breast and
head-neck cancer patients, are overlaid with the
individual in vitro radiosensitivity index and the in vivo
tissue radiosensitivity detected during the follow-up. We
expect to identify a 5-10 gene network determining the
individual radiophenotype.
Material and Methods
1. Criteria for patient enrolling: breast or head-neck
cancer diagnosis; exclusion of congenital syndromes
predisposing to radiosensitivity; patients not previously
treated with chemo-radiotherapy; age > 18 years; patient
agreement to undergo follow-up; informed consent. 2. G2-
assay for the prediction of radiosensitivity: an individual
radiosensitivity index (IRS) is calculated according to the
G2-chromosomal radiosensitivity and the G2 checkpoint
efficiency. Details of the protocol are in 1. 3. Gene
expression analysis: Gene expression analysis is performed
by quantitative real-time PCR (qRT-PCR) on total RNA
isolated from blood drawns harvested before the
administration of the first fractioned dose of RT and 24 h
later. 4. Statistical analysis: Anova test is performed to
analyse the differential expression across IRS classes and
a Spearman analysis is performed to assess correlation
between expression and IRS index.
Results
The expression of DDB2, GADD45A, CDKN1A, and ATM
genes following irradiation 2,3 has been correlated with the
in vitro IRS evaluated by the G2-chromosomal assay; at
present, a positive correlation between ATM expression
and IRS could be inferred despite the unavoidable inter-
individual variability. The analyses on other DDR genes are
in progress.
Conclusion
The innovation of this study is the use of a molecular
biology approach to assess patient radiosensitivity before
RT, in the frame of an integrated approach between
clinicians and biologists.
References
1. Pantelias GE. & Terzoudi G. I. Radiother. Oncol. 101
(2011).
2. Mognato M. & Celotti L. Mutat. Res. Mol. Mech.
Mutagen. 578 (2005).
3. Girardi C. et al. PLoS One 7 (2012).
Poster: Radiobiology track: Radiobiology of lung cancer
PO-0975 Clinical utilization of the radiation-hypoxia-
induced abscopal/bystander effect in lung cancer
S. Tubin1,2, S. Gupta3, A.M. Mansoor4
1KABEG Klinikum Klagenfurt, Radioonkologie, Klagenfurt,
Austria
2Sylvester Comprehensive Cancer Center- University of
Miami Leonard Miller School of Medicine, Department of
Radiation Oncology, Miami, USA
3Georgia Cancer Center- Augusta University- Augusta-
GA- USA, Health Sciences, Augusta, USA
4National Cancer Institute- National Institutes of Health,
Radiotherapy Development Branch- Radiation Research
Program- Division of Cancer Treatment and Diagnosis,
Rockville, USA
Purpose or Objective
To report on initial results in a small series of consecutive
patients treated with high-dose hypofractioneted
radiotherapy (1-3 fractions) in the treatment of
oligometastatic patients with large tumor masses focusing
on application of results previously obtained by in vitro
studies on radiation-induced abscopal/bystander effect.
Our previous study (unpublished data) focused on
targeting tumor hypoxia that induced a strong
abscopal/bystander effect. We provide data that support
the contention that high-dose radiation to the part of a
large gross tumor volume (GTV) has the potency to induce
a robust bystander effect, as well as abscopal (distant)
effects.
Material and Methods
In the in vitro studies conditioned medium-transfer
experiments with A-549, H-460 lung cancer cells, as well
as their hypoxic clones (A-549HR, H-460HR), were
performed. All the cells were irradiated in normoxic or
hypoxic conditions with 10Gy single dose and cell growth
and survival were monitored by real time cell electronic
sensing (RTCES) System and colony forming assay,
respectively. In the clinical study, 5 consecutive
oligometastatic patients with large hypoxic cancers of
lung (3), neck (1) and mediastinum (1) were treated with
high dose radiotherapy using high-energy photons. All
lesions were irradiated partially by targeting the central
hypoxic region (Figure 1), which corresponded to 30% of
total GTV (Mean GTV volume 181 cc, mean diameter 6, 8