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S482
ESTRO 36 2017
_______________________________________________________________________________________________
1
San Raffaele Scientific Institute, Medical Physics, Milan,
Italy
2
San Raffaele Scientific Institute, Radiotherapy, Milan,
Italy
3
San Raffaele Scientific Institute, Nuclear Medecine,
Milan, Italy
Purpose or Objective
To investigate the predictive role of early changes of
18
F-
fluorodeoxyglucose (FDG) positron emission tomography
(FDG-PET) based biomarkers in locally advanced
pancreatic carcinoma (LAPC) patients (pts) treated with
induction and concomitant chemo-radiotherapy (CRT) on
overall survival (OS), local relapse free survival (LRFS),
distant relapse free survival (DRFS) and progression free
survival (PFS).
Material and Methods
Data of 39 pts included in an Institutional trial were
considered. Most pts (92%) received neoadjuvant
chemotherapy, followed by CRT. Pts received 44.25Gy in
15 fractions to the tumor: a simultaneous integrated boost
(SIB) to the sub-volume infiltrating the great abdominal
vessels up to 48-58Gy was delivered in 17/39 pts. FDG-
PET-CT was performed in all pts before (PET_pre) and
after CRT (PET_post), at a median time of 3-months after
the end of CRT. The predictive value of the % difference
of FDG-PET parameters between PET_post and PET_pre
was investigated, including maximum standard uptake
value (∆SUVmax), metabolic tumor volume (∆MTV) and
total lesion glycolysis (∆TLG), these last twos estimated
considering different uptake thresholds (40-50-60%) of
SUVmax. The % difference between gastrointestinal
cancer-associated antigen (GICA) levels measured at
roughly the same timing of PET scan (pre and post) was
also considered. For each parameter, median ∆ values
were used to categorize the pts in high vs low risk groups:
logrank tests and univariable Cox regression analyses were
performed to assess the prognostic value of the considered
parameters on OS, LRFS, DRFS and PFS.
Results
The median follow-up was 11 months (range: 3.7-106); the
median age was 63 years (35-84). Median OS, LRFS, DRFS
and PFS after the start of CRT were 22, 10, 4.3, 5.3
months, respectively. No uptake was present at PET_pre
in 9 pts: a longer median time to progression for PET
negative pts (9.0 vs 3.7 months,
p
=0.06) was found
compared to pts with positive PET_pre. Focusing on the
30/39 pts with positive PET-pre, ∆MTV-60 was the most
significant predictor of LRFS (
p
=0.007; RR=0.16) and PFS
(
p
=0.04; RR=0.41). Median LRFS were 4.3 and 23 months
for pts with ∆MTV-60< 35% and pts with ∆MTV-60> 35%,
respectively
(
p
=0.002;
RR=3.8,
Figure1);
the
corresponding median PFS were 3.2 vs 6.7 months (
p
=
0.03; RR=2.2, Figure2). ∆TLG-50 and ∆TLG-60 showed
borderline significance in predicting OS (
p
= 0.05;
RR=0.33). No correlation was found between the %
variation of PET parameters and DRFS while the % change
of GICA levels was a significant predictor (
p
=0.03;
RR=0.28).
Conclusion
The early assessment of FDG-PET biomarkers response
predicts clinical outcome in LAPC pts, except DRFS. The
early variation of GICA values predicts DRFS suggesting
that the integration of the information concerning early
changes of PET biomarkers and GICA may be useful in
identifying patients at higher risk of early local and/or
distant relapse and to discriminate the pattern of relapse.
PO-0887 Experimental validation of a 3D model to
simulate FMISO spatial retention in HNSCC tumor
xenografts
L.J.M. Wack
1
, A. Menegakis
2
, R. Winter
1
, S. Boeke
2
, K.
Trautmann
3
, A. Leun
1
, M. Krueger
4
, B. Pichler
4
, D.
Mönnich
1
, D. Zips
2
, D. Thorwarth
1
1
Clinic for Radiation Oncology- University Hospital
Tübingen, Section for Biomedical Physics, Tübinge n,
Germany
2
University Hospital Tübingen, Department of Radiation
Oncology, Tübingen, Germany
3
University Hospital Tübingen, Department of Pathology
and Neuropathology, Tübingen, Germany
4
Preclinical Imaging and Radiopharmacy, Werner Siemens
Imaging Center, Tübingen, Germany
Purpose or Objective
Tumor hypoxia is prognostic for poor outcome after
radiotherapy (RT). A method for non-invasi ve assessment
of hypoxia is PET using hypoxia radiotracers such as FMISO.
For this study, we evaluated a tool to simulate 2D and 3D
FMISO accumulation on realistic vessel architectures,
which can be compared against experimental
pimonidazole (pimo) stainings of the same tumor.
Material and Methods
Dynamic PET/MR imaging was performed in FaDu tumors
(human HNSCC) grown in the right hind leg of nude mice
for about 5 weeks, using an injected FMISO activity of
~12MBq. Pimo and hoechst 33342 were injected 1h and
1min prior to tumor excision, respectively, to allow
staining for tumor hypoxia and perfusion status of blood
vessels. After excision, two tumors were snap frozen and
the central part was cut into 120 consecutive sections of
10µm. Immunofluorescence staining was performed for
pimo and endothelial marker CD31. Sections were
subsequently scanned on a Zeiss Axiovert fluorescence
microscope to detect pimo, CD31 and hoechst. The
fluorescence images were rigidly registered, manually