ESTRO 36 Abstract Book

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S167 ESTRO 36
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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[18F]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. Heerkens1, M. Van Vulpen1, B. Erickson2, O.
Reerink3, M. Intven1, C.A.T. Van den Berg1, I.Q.
Molenaar 4, F.P. Vleggaar5, G.J. Meijer1
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
may lead to better palliation and possibly increase survival
with the advantage of a short overall treatment time. The
superior soft tissue contrast of MRI might improve tumour
contouring and MRI is capable of tumour motion
quantification. We want to investigate the technical
feasibility and safety of MRI-guided SBRT for LAPC.
Material and Methods
From July 2013 to January 2016, 20 patients with LAPC or
medically unresectable pancreatic cancer without distant
metastasis were included in this study (Table). A custom
made abdominal corset was manufactured to reduce
breathing induced tumour motion. Contouring of the gross
tumour volume (GTV) and organs at risk (OARs) was
performed on 4D treatment planning CT and
multiparametric MRI. A GTV-to-PTV margin of 3 mm was
applied. We quantified tumour motion with cine MRI. After
treatment planning, the static dose distribution was
convolved with the cine MRI based motion trajectory to
simulate and evaluate the delivered dose to the GTV, PTV,
and OARs. SBRT was carried out up to a dose of 24 Gray in
3 fractions in one week. Online position verification was
performed with 4D CBCTs, with 4D matching based on gold
fiducial markers at the midventilation position.
Results
All patients underwent uncomplicated endoscopic fiducial
marker placement. Tumours and OARS were clearly visible
with contrast enhanced CT and multiparametric MRI
(Figure). On the 4D planning CT and on the 4D CBCT scans,
the fiducial markers were clearly visible. The corset
decreased peak-to-peak tumour motion in craniocaudal
direction on average from 11.3 to 7.2 mm. With
incorporation of the tumour motion trajectory, the dose
distribution was blurred and, in this way, the actual
delivered dose was simulated. In all patients, an adequate
dose distribution was achieved with acceptable dose in the
OARs (Table). Position verification based on 4D marker
matching was feasible. No grade 3 or higher treatment
related toxicity was observed in these patients to date.