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ESTRO 36
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Conclusion
Tumor voxel metabolic ratio determined us ing multiple
FDG PET images can be used to assess tumor voxel dose
response, SF2, which shows an excellent predictive value
for tumor local radioresistance and failure. Our results
demonstrate that a heterogeneous dose distribution in
tumor should be prescribed to optimize cancer
radiotherapy. Tumor voxel TMR determined at the early
treatment will be good bio-parametric matrix to
determine a new tumor dose prescription function at the
voxel level for the treatment of adaptive dose-painting-
by-number.
PO-0886 Early changes of FDG-PET markers predict the
outcome after chemo-radiotherapy for pancreatic
cancer
S. Broggi
1
, P. Passoni
2
, E.G. Vanoli
3
, C. Fiorino
1
, G.M.
Cattaneo
1
, C. Gumina
2
, P. Mapelli
3
, E. Incerti
3
, L.
Gianolli
3
, N. Slim
2
, M. Picchio
3
, R. Calandrino
1
, N.G. Di
Muzio
2
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.