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ESTRO 36 2017
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Conclusion
Since the start of IORT service in Aug 2013, we have
delivered 146 treatment fields to 130 patients with limited
toxicity and excellent local control. In a busy service, IORT
is not always a straightforward electron treatment, and
staff experience and adequate data is important.’
EP-1580 Dosimetric comparison between 3D-
conformal radiation therapy and VMAT in Total
Lymphoid Irradiation
C. Ferrer
1
, C. Huertas
1
, A. Escribano
1
, R. Plaza
1
, R.
Morera
2
, A. Serrada
2
1
Hospital universitaria La Paz, Radiofísica y
Radioprotección, Madrid, Spain
2
Hospital universitaria La Paz, Oncología Radioterápica,
Madrid, Spain
Purpose or Objective
Total Lymphoid Irradiation (TLI) is used in the
management of pediatric allogeneic hematopoietic stem
cell transplantation (HSCT). This study compares the
conventional 3D-conformal radiation therapy (3DCRT)
anteroposterior-posteroanterior (AP-PA) technique with
volumetric-modulated arc therapy (VMAT) for TLI.
Material and Methods
Treatment plan for conventional AP-PA technique was
performed with XiO treatment planning system (CMS, v.
5.00.01) and VMAT plan was performed with Elekta
Monaco treatment planning system (v. 5.00.00), optimized
using biological and physical based cost functions, on an
Elekta Synergy linear accelerator equipped with a 160-leaf
Agility MLC.
Prescription dose was 8 Gy in 2Gy daily fractions. Patient
was in supine position over a custom shaped vacuum bag
device, along with an aquaplast mask for head position
reproducibility. The arms were extended laterally. VMAT
treatment consisted in 2 isocenters, with 4 cm overlap
length and 2 partial arcs (290° - 70° and 135 - 210°) each.
Linac treatment couch was included in the calculation.
For both techniques, PTV coverage, conformation index
(CI), conformation number (CN) and Heterogeneity index
(HI) have been compared, as well as doses to organs at risk
(OAR) and integral body dose.
Results
Table 1 shows the results obtained for the PTV and OARs.
PTV coverage with both techniques was adequate (V95%=
91.5% and 95.3% for 3DRT and VMAT respectively), HI were
similar, but conformation indices were better with VMAT
technique. VMAT also improved the doses to the lungs, the
heart and the spinal cord. Heart volume receiving 5 Gy or
more (V
5Gy
) and receiving 8 Gy or more (V
8Gy
) was
considerably lower in VMAT plan. Integral dose, calculated
by the product of mean dose to the patient without the
PTV and the irradiated volume was 11% lower in the VMAT
plan and the mean skin dose 33% lower
.
Conclusion
Although both techniques achieve similar PTV coverage,
VMAT plan shows higher level of conformation, with
considerably lower mean skin dose and integral dose in
spite of the low-dose spread. Doses to OAR are also lower
with VMAT, specially the heart. VMAT technique can be
very beneficial for pediatric patients undergoing TLI, with
lower late organ toxicity.
EP-1581 Dosimetric comparison of treatment plans for
pancreatic cancer: 3DCRT, IMRT and VMAT
P. Trecca
1
, M. Fiore
1
, B. Floreno
1
, R. D'Angelillo
1
, L.
Trodella
1
, A. Mameli
1
, E. Infusino
1
, C. Greco
1
, L.
Trodella
1
, S. Ramella
1
1
Campus Biomedico University, Department of Radiation
Oncology, Roma, Italy
Purpose or Objective