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schemes. With the use of SBRT there is also a need for
accurate target delineation. The hypothesis is that MRI
allows for better visualization of the extend of bone
metastases in mRCC for contouring in the context of
stereotactic treatment planning.
Material and Methods
From 2013 to 2016, nine consecutive patients who
underwent SBRT for RCC bone metastases at our center
were included. A planning CT and MRI were performed in
radiotherapy position according to our clinical protocol.
CT images were performed at 1 mm slice thickness on a
large bore CT scanner (Philips, The Netherlands). In
addition, all patients underwent a 1.5 Tesla MRI scan
(Philips Ingenia, The Netherlands) at 1.1 – 4 mm slice
thickness. For every patient, T1-weighted images were
acquired in transversal and sagittal direction, including a
transversal mDIXON scan, as well as T2-weighted images
in transversal and sagittal direction, and diffusion
weighted images (DWI) according to our clinical MRI
protocol. Gross tumor volumes (GTV) in both CT and MRI
were delineated. Contouring was performed by a
specialized radiation oncologist, based on local consensus
contouring guidelines (T1 images were used for target
delineation aided by the information derived from the T2
and
DWI
sequences).
In both CT and MRI the GTV volumes, conformity index (CI)
and distance between the centers of mass (dCOM) were
compared. Statistical differences in volumes between CT
and MRI were tested with Wilcoxon rank sum test.
Results
Nine patients with 11 RCC bone metastases were
evaluated. The volumes of the lesions on MRI were larger
compared to the CT, for all but one lesion (Table 1). This
lesion was comparable in size on MRI and CT. Two visual
examples of the difference in delineation are shown in
Figure 1. The median GTV volume on MRI was 33.39mL
(range 0.2mL – 247.6mL), compared to 14.87mL on CT
(range 0.2mL – 179.4mL). The difference in volume as
delineated on CT and MRI was statistically significant
(p=0.005). The CI in the different lesions varied between
0.08 and 0.75. The dCOM varied between 0.78 and 13.34
mm.
Conclusion
Contouring of RCC bone metastases on MRI resulted in both
clinically and statistically significant larger lesions
compared with CT. MRI seems to represent the extend of
the GTV in RCC bone metastases more accurately, possibly
due to improved visualization of bone marrow infiltration.
Contouring based on CT-only could result in an
underestimation of the actual tumor volume, which may
cause an under dosage of the GTV in SBRT treatment
plans.
EP-1391 Digestive toxicity after conformal
radiotherapy for palliative cervico-thoracic spinal
metastases
G. Peyraga
1
, D. Caron
1
, Y. Metayer
2
, Y. Pointreau
3
, F.
Denis
3
, G. Ganem
3
, C. Lafond
3
, S. Roche
3
, O. Dupuis
3
1
Institut de Cancérologie de l'Ouest, Radiation Therapy,
Angers, France
2
Centre Jean Bernard, Medical Physics, Le Mans, France
3
Centre Jean Bernard, Radiation Therapy, Le Mans,
France
Purpose or Objective
The palliative treatment of cervico-thoracic spinal
metastases is based on a conformal radiotherapy (CRT),
delivering 30 Gy in 10 fractions (5 days a week for 2
weeks). Digestive toxicities (esophagitis, nausea and
vomiting) are common after these radiations and cause a
clinical impact probably underestimated in patients. We
performed a retrospective monocentric study of early
digestive toxicities occurred secondarily to palliative CRT
of cervico-thoracic spinal metastases.
Material and Methods
All patients receiving palliative CRT at Jean Bernard
Center from January 2013 to December 2014 of spinal
metastases (all primitive tumors were included) between
the fifth cervical vertebra (C5) and 10th thoracic vertebra
(T10) for which clinical follow-up was available beyond 3
months were included. Re-irradiations were excluded.
CRT was delivered by a linear accelerator (CLINAC,
Varian). Premedication to prevent digestive toxicities was
not recommended. Adverse events (esophagitis and
nausea/vomiting < 3 months) were evaluated according
the NCI-CTCae (version 4).
Results
From January 2013 to December 2014, 128 patients met
the study criteria. The median age was 69.6 years [31.8;
88.6]. The majority (84.4%) patients received a dose of 30
Gy in 10 fractions. The median treatment duration was 13
days [3-33]. Forty patients (31.3%) experienced grade 2 or
3 of esophagitis (35 grade 2 (27.4%) and 5 grade 3 (3.9%)),
and 8 patients (6.3%) experienced grade 2 or 3 of nausea
or vomiting (6 grade 2 (4.7%), 1 grade 3 (0.8%) and 1 grade
4 (0.8%)). The risk of digestive toxicities seems to be
related to spinal localization of metastases (38.5% of
grade 2 or 3 esophagitis if radiation from C5 to T4 versus
31.2% if radiation from T5 to T10, and 87.5% of nausea and
vomiting concerned T9 or T10) and to the number of