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mean pathologic node volume at diagnosis was 3.4±5.8
cm
3
. The mean EBRT and nodal boost doses were 44.3±0.9
Gy and 10.0±2.9 Gy respectively. The mean IGABT
contribution to pelvic nodes was 4.2±2.6 Gy. Finally the
mean total dose to lymphadenopathies was 55.3±5.6 Gy.
Concomitant chemotherapy was administrated in 96.5% of
the patients. After a median follow-up of 33.5 months, 20
patients (17.4%) experienced relapses in nodes initially
considered pathologic at diagnosis (local relapse). Among
them recurrences were observed in a total of 44 nodes
(15.3%). The mean time from treatment completion to
relapse was 9.0±11.8 months.
There was no significant relationship between the dose
delivered to pathologic nodes and local control probability
(p=0.38). Univariate analyses tested various factors:
subtypes (SCC versus others, p=0.35), concomitant
chemotherapy (p=0.39), use of SIB (p=0.07), volume at
diagnosis (threshold: 3 cm
3
, p<0.0001) and dose (≥ 57.5
Gy, p=0.039). The last three factors were entered in a
multivariate analysis. Volume (HR=8.2, 4.0-16.6,
p<0.0001) and dose (HR=2, 1.05-3.9, P=0.034) remained
independent, whereas SIB was not (p=0.99). Subsequent
Probit analysis combining dose and volume showed
significant relationships with the probability of local
control (Figure).
Conclusion
The initial volume was the main prognostic factor of
control in pathologic lymph nodes. A dose superior to 57.5
Gy was also associated with a better local control
probability. Further studies are required to refine these
findings.
Poster Viewing : Session 7: Upper and lower GI
PV-0320 Stereotactic body radiotherapy for liver
metastases based on functional treatment planning
M.M. Fode
1
, J. Petersen
2
, E. Worm
2
, M. Sørensen
3
, K.
Bak-Fredslund
3
, S. Keiding
3
, M. Høyer
4
1
Aarhus University Hospital, Department of Oncology,
Aarhus C, Denmark
2
Aarhus University Hospital, Department of Medical
Physics, Aarhus C, Denmark
3
Aarhus University Hospital, Department of Nuclear
Medicine & PET Centre and Department of Hepatology
and Gastroenterology, Aarhus C, Denmark
4
Aarhus University Hospital, Danish Centre for Particle
Therapy, Aarhus C, Denmark
Purpose or Objective
2[
18
F]fluoro-2-deoxy-D-galactose (FDGal) is a hepatocyte-
specific positron emission tomography (PET) tracer. It was
used as a marker for hepatocyte function for applying
functional treatment planning (FTP) to minimize the
radiation dose to the normal liver tissue. We report the
results of a cohort of patients treated with FTP-
stereotactic body radiotherapy (SBRT) for liver
metastases.
Material and Methods
Fourteen patients referred for SBRT for liver metastases
from colorectal cancer were included in the study
between December 2013 and August 2016. Nine patients
were irradiated for a solitary metastasis and five patients
for two (n=4) or three (n=1) metastases. The mean
cumulated CTV was 70.3 cc (range 2.0 - 189.7 cc). FDGal
PET/CT was performed at baseline and one month post-
treatment. The liver was divided into nine iso-functioning
volumes based on radioactivity concentration SUV of
FDGal on the baseline FDGal PET/CT and transferred to
the planning CT using deformable co-registration. The
prescribed mean dose to the CTV was 45-60 Gy in 3-6
fractions. The post-treatment FDGal PET/CT was used for
evaluation of radiation dose-response for the normal liver
tissue.
Results
FTPs were created and applied for all patients and all
plans met the predefined dose-volume constraints with
the exception of a soft constraint of mean dose to the
liver-CTV that was not met in three patients. Eight
patients (57%) were treated with local therapy for liver
metastases before inclusion in the present study (surgery
n=1; SBRT n=1; combined local therapy n=6. No severe
(CTCAE 4.0 grade 3-5) acute morbidity was registered.
Teen grade 1 gastrointestinal and six grade 1-2 non-
gastrointestinal acute morbidities were registered. No
patients had liver-related morbidity. Analysis of the post-
treatment FDGal PET/CT revealed a dose-dependent
depression in hepatocyte function measured in SUV of
FDGal uptake in the irradiated normal liver tissue.
Conclusion
The study shows feasibility for FTP in patients with
colorectal liver metastases referred for SBRT using FDGal
PET/CT as a marker for hepatocyte function and the
radiation dose to the normal liver tissue was minimized
without compromising the organs at risk. The acute
morbidity was minimal.
PV-0321 MRI guided stereotactic radiotherapy for
locally advanced pancreatic cancer
H.D. Heerkens
1
, M. Van Vulpen
1
, B. Erickson
2
, O.
Reerink
3
, M. Intven
1
, C.A.T. Van den Berg
1
, I.Q.
Molenaar
4
, F.P. Vleggaar
5
, G.J. Meijer
1
1
UMC Utrecht, Radiation Oncology Department, Utrecht,
The Netherlands
2
Medical College of Wisconsin, Radiation Oncology
Department, Milwaukee, USA
3
Isala Clinic, Radiation Oncology Department, Zwolle,
The Netherlands
4
UMC Utrecht, Surgery Department, Utrecht, The
Netherlands
5
UMC Utrecht, Gastroenterology Department, Utrecht,
The Netherlands
Purpose or Objective
Patients with locally advanced pancreatic cancer (LAPC)
show a poor survival due to limited effective therapeutic
options. Stereotactic radiotherapy (SBRT) may delay the
development of metastasis and physical discomfort, and it