ESTRO 36 Abstract Book

224 / 1082

S211 ESTRO 36 2017
_______________________________________________________________________________________________
Purpose or Objective
Radio(chemo)therapy is a crucial treatment modality for
head and neck squamous cell carcinoma (HNSCC) and
radioresistance is a major reason for therapy failure and
is related to tumour recurrence and poor prognosis.
However, the underlying molecular mechanisms are
largely unknown. In order to gain knowledge on this
fundamental and clinically relevant feature, we
established an in vitro model of CAL-33 HNSCC cell line
subclones with different radiosensitivity. The main aim of
the study was to identify signalling pathways and key
regulators of radioresistance by static and dynamic global
mRNA expression analyses followed by gene association
network (GAN) reconstruction and pathway enrichment
analyses.
Material and Methods
Subclones with altered radiosensitivity were generated by
fractionated irradiation of the parental CAL-33 cells and
colony formation assays were performed to confirm the
differences in radiosensitivity. Selected subclones were
characterized at the genome and transcriptome levels by
SKY, array CGH, and mRNA-microarray analyses.
Temporally differentially expressed genes upon irradiation
were identified using natural cubic spline regression
modelling on time-course transcriptome data. Moreover,
early and late responding genes were determined. GANs
were reconstructed using a partial correlation-based
approach. Pathway enrichment analyses were conducted
employing the Reactome pathway database. Microarray
gene expression data were technically validated by qRT-
PCR.
Results
The characterization of two subclones with enhanced
radiation resistance (RP) and enhanced radiosensitivity
(SP) revealed distinct genomic and transcriptomic changes
compared to the parental cells. Interestingly, the
expression of the endogenous retrovirus ERV3-1 in
response to irradiation has been observed in all of the CAL-
33 cells, suggesting a role in the radiation response of
HNSCC cells. Differentially expressed genes after
irradiation shared by both subclones pointed to important
pathways of the early and late radiation response,
including senescence, apoptosis, DNA repair, Wnt,
PI3K/AKT, and Rho GTPase signalling. The analysis of the
most important nodes of the GANs revealed pathways
specific to the radiation response in different phenotypes
of radiosensitivity. Exemplarily, for the RP subclone the
senescence-associated secretory phenotype (SASP)
together with GPCR ligand binding were considered as
crucial.
Conclusion
Our study presents comprehensive gene expression data of
CAL-33 subclones with different radiation sensitivity.
Based on these data GANs have identified known to be
linked to the radiation response phenotypes. The resulting
GANs and pathways associated with the resistant
phenotype are of special interest and include SASP
together with GPCR ligand binding. The identified
pathways may represent key players of radioresistance,
which could serve as potential targets for molecularly
designed, therapeutic intervention.
OC-0400 Prognostic impact of tumor infiltrating
lymphocytes and PD-L1 expression in head and neck
cancers
D. Ou1,2, J. Adam3, I. Garberis3, P. Blanchard1, F.
Nguyen1, A. Levy1, O. Casiraghi 3, P. Gorphe4, I. Breuskin4,
F. Janot4, S. Temam 4, J. Scoazec 3, E. Deutsch1, Y. Tao1
1 Institut Gustave Roussy, Department of Radiation
Oncology, Villejuif, France
2 Fudan University Shanghai Cancer Center, Department
of Radiation Oncology, Shanghai, China
3 Institut Gustave Roussy, Department of Pathology,
Villejuif, France
4Institut Gustave Roussy, Department of Head and Neck
Oncology, Villejuif, France
Purpose or Objective
The aim of the present study was to investigate the
prognostic value of CD8+, FoxP3+ tumor infiltrating
lymphocytes (TILs) and PD-L1 expression in patients with
head and neck squamous cell carcinoma (HNSCC) treated
with definitive radiotherapy combined with cisplatin or
cetuximab.
Material and Methods
Immunohistochemistry for CD8, FoxP3 was performed on
formalin or formalin-acetic acid-alcohol fixed, paraffin-
embedded, pretreatment tissue samples of 77 patients
from a previously reported HNSCC cohort. PD-L1 results
were evaluable in 38 patients only. The Kaplan–Meier
method, univariate and multivariate analyses (MVA), were
used to analyze the correlations of these biomarkers
expression with patient/ tumor characteristics and
treatment outcomes.
Results
CD8+ and FoxP3+ TIL densities differed significantly by
HPV/p16 status, primary tumor location, T stage, and N
stage. High CD8+ TIL level was identified in MVA as an
independent prognostic factor for improved PFS (HR=0.3,
95%CI 0.1-0.7, p = 0.01) and there was a non-significant
trend for better OS (HR=0.4, 95%CI 0.2-1.1, p = 0.07). High
FoxP3+ TILs and PD-L1+ correlated with a favorable OS in
the UVA, but not in the MVA. In p16+ subgpopulation, high
CD8+TILs patients had improved 5-year OS compared with
low CD8+TILs patients (100% vs. 88.9%, p=0.049), and PD-
L1+ patients had improved 3-year OS compared with PD-
L1- ones (100% vs. 50.0%, p=0.01). In low CD8+ TILs
tumors, 5-year LRC of patients treated with CRT was
improved vs. those with BRT (92.3% vs. 51.0%, p=0.01),
while in high CD8+ TILs, no significant difference with CRT
vs. BRT.
Conclusion
Immune factors in the tumor microenvironment correlated
with HNSCC clinicopathological features and survival
outcomes. CD8+ TILs were independently correlated with
an improved clinical outcome in HNSCC patients and may
potentially be correlated with different treatment
outcome by cisplatin or cetuximab. Further work is
warranted to validate these findings in a larger
independent cohort and investigate the potentially
associated causal mechanisms.
Symposium: Experimental therapies
SP-0401 Grid therapy: past, present, and future
A. Siegbahn1
1Stockholm University, Department of Physics,
Stockholm, Sweden
Irradiation of tumours with grids of x-ray beams was
proposed already about a decade after W.C. Röntgen's
original discovery of x rays. Grid therapy was thereafter
used in the clinic during the first half of the past century,
mainly to reduce the incidence of radiation-induced skin
reactions. The beam elements (forming the grid) were
approximately 1 cm wide and were separated with a
similar distance to form a chessboard-shaped irradiation
pattern at the patient surface. The dose distribution in the
target volume was alternating between very high peak-
and low valley-doses. Later, it was realized that the
toxicity was also reduced for other organs located beneath
the skin, if leaving tissue volumes, in-between the
radiation beam elements, unirradiated. In recent years, a
large cohort of head-and-neck, thoracic and abdominal
cancer patients have been treated with the grid technique
using high-energy linac-generated photon beams. Grid
therapy has normally been considered only when other