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S361
ESTRO 36 2017
_______________________________________________________________________________________________
3
Radiotherapy Institute Friesland, Radiation Oncology,
Leeuwarden, The Netherlands
4
The Netherlands Cancer Institute, Radiotherapy,
Amsterdam, The Netherlands
Purpose or Objective
Delineation variation of esophageal tumors remains a large
source of geometric uncertainty. Recent studies trying to
decrease esophageal tumor delineation variation by
adding PET/CT information showed no significant
reduction. With future studies focusing on dose
escalation, a correct gross tumor volume (GTV)
delineation will become more important. In the present
study, we investigated the inter- and intra-observer
variation in esophageal GTV delineation and the impact of
fiducial markers on this variability.
Material and Methods
Ten esophageal cancer patients were included in this
study, with at least 2 fiducial markers implanted at the
cranial and caudal tumor border, visible on planning CT
(pCT). Two GTV delineation phases were performed by
five dedicated gastrointestinal radiation-oncologists
independently. In-house designed software digitally
removed the fiducial markers from the pCTs. Phase 1
consisted of a GTV delineation on the resulting marker-
less pCTs (denoted pCT-m). Phase 2 consisted of a GTV
delineation on the original (e.g., with markers) pCTs
(denoted pCT+m). Phase 1 and 2 were executed twice to
determine intra-observer variability. As general metrics
for inter-observer variability; volumes, generalized
conformity indices (CI
gen
; 1 indicating full overlap and 0
indicating no overlap) and delineation variation (cranio-
caudal (CC) variation and overall observer variation
expressed as standard deviations (SDs)) were calculated.
Intra-observer variability was determined in terms of
overall observer variation. A Wilcoxon signed-rank test
was performed to compare delineation phases
(significance level α=0.05).
Results
For all delineated volumes, the results of the mean
volumes, CI
gen,
CC delineation variation and overall
observer variation, of all 10 patients are listed in Table 1.
Inter-observer overall observer variation (1SD) was 0.64
cm and 0.28 cm in phase 1 and phase 2, respectively
(
p
=0.027
)
. CC delineation variation (1SD) was 1.48 cm for
phase 1 and 0.43 cm for phase 2 (
p
=0.004
)
. CI
gen
was
significantly larger in phase 2 (0.54 vs 0.68;
p
=0.006
)
.
Intra-observer overall observer variation (1SD) was 0.44
cm and 0.26 cm, for phase 1 and phase 2 respectively,
significantly reduced with the aid of fiducial markers
(
p
=0.006).
Conclusion
Large inter- and intra-observer variation in delineation of
esophageal tumors was found when using marker-less
pCTs. Presence of fiducial markers at CC tumor borders,
significantly improved all investigated delineation
variation parameters. Since fiducial markers only assist
with the determination of the cranial and caudal tumor
border, the largest variation reduction (1SD = 1.48 cm to
0.43 cm) was logically seen in the CC delineation
variation. Our results endorse the use of fiducial markers
in esophageal GTV delineation, consequently reducing
geometric uncertainty in esophageal cancer radiotherapy.
PO-0698 Phase II study of induction chemotherapy
followed by radiochemotherapy in pancreatic cancer
M. Fiore
1
, R. D'Angelillo
1
, B. Floreno
1
, P. Trecca
1
, L.
Trodella
1
, A. Iurato
1
, L. Trodella
1
, R. Coppola
2
, S.
Ramella
1
1
Campus Biomedico University, Department of Radiation
Oncology, Roma, Italy
2
Campus Biomedico University, Department of General
Surgery, Roma, Italy
Purpose or Objective
To evaluate the safety and efficacy of induction
gemcitabine and oxaliplatin followed by a high weekly
dose of gemcitabine-based radiochemotherapy in patients
with borderline resectable or unresectable locally
advanced pancreatic cancer.
Material and Methods
From January 2012 through January 2015, 41 patients with
pancreatic cancer were included in the study. In all cases
an accurate pre-treatment staging was performed.
Patients received chemotherapy with gemcitabine 1000
mg/mq and oxaliplatin 100 mg/mq every 14 days for four
doses. Patients without disease progression after restaging
received conformal radiation therapy and concurrent
gemcitabine at the dose of 600 mg/mq weekly.
Results
Further to the results of the pre-treatment workup, seven
patients (17%) were excluded from the protocol because
of the evidence of metastatic disease, and thus a total of
34 patients were consequently enrolled. Induction
chemotherapy was well tolerated. Five patients (14.7%)
experienced disease progression after induction
chemotherapy.Twenty-seven patients completed the
therapy protocol. Only haematological grade 3-4 toxicities
were observed. Nineteen patients were evaluated through
surgical exploration and fifteen patients (55.5%)
underwent surgical radical resection. With a median