ESTRO 36 Abstract Book

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S839 ESTRO 36 2017
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Being completely involved into the target volume such
OARs as optic chiasm and brain stem including their PRVs
were added to “Target Constraints” tab along with other
PTVs for better dose control in this areas. For the most
conformal treatment plan deliverable in a reasonable
time, all plans were generated using a 2.5 cm field width,
pitch 0.295 and the final modulation factor of 2.1. The
template was made within the treatment planning system
(TPS).
All previously treated patients were replaned and target
coverage was analyzed for PTV1 and PTV2_nR in terms of
homogeneity index (HI) and conformation number (CN),
where TV95% - tumor volume covered with 95% isodose, TV
– tumor volume, V95% - volume of 95% isodose.
The results are shown in the table below.
Conclusion
The development and implementation of standard
technique for WBRT with SIB allowed us to much faster
treatment planning performance using automated
workflows for additional structures creation and TPS
template for lower machine time used. The treatment
time was decreased from 8.09±2.98 min to 6.85±0.95 min
(p=0.05). New plans showed good homogeneity (HI
0.071±0.047 for PTV1 and 0.072±0.015 for PTV2_nR) and
conformity (CN 0.794±0.169 for PTV1 and 0.82±0.077 for
PTV2_nR) (p=0.05) with good OAR sparing.
EP-1577 Hippocampus-sparing whole-brain IMRT and
simultaneous integrated boost to multiple brain
metastases
S. Cilla1, F. Deodato 2, M. Ferro 2, G. Macchia2, A. Ianiro1,
V. Picardi2, M. Boccardi2, M. Ferro2, S. Cammelli3, A.
Arcelli 3, E. Farina3, L. Giaccherini3, G.P. Frezza4, V.
Valentini5, A.G. Morganti 3
1 Fondazione di Ricerca e Cura "Giovanni Paolo II"-
Università Cattolica del Sacro Cuore, Medical Physics
Unit, Campobasso, Italy
2 Fondazione di Ricerca e Cura "Giovanni Paolo II"-
Università Cattolica del Sacro Cuore, Radiation Oncology
Unit, Campobasso, Italy
3 Università di Bologna, Radiation Oncology Center-
Department of Experimental- Diagnostic and Specialty
Medicine - DIMES, Bologna, Italy
4 Ospedale Bellaria, Radiation Oncology Department,
Bologna, Italy
5 Policlinico Universitario "A. Gemelli"- Università
Cattolica del Sacro Cuore, Radiation Oncology
Department, Roma, Italy
Purpose or Objective
High dose irradiation to hippocampus is critical in
determining neurocognitive function (NCF) outcomes. We
evaluated the feasibility of intensity-modulated whole-
brain radiotherapy (IMRT) and simultaneous integrated
boost (SIB) to multiple brain metastases (BMs) to generate
hippocampus-sparing plans.
Material and Methods
5 patients with a total of 16 BMs who previously underwent
whole brain radiotherapy with boost to multiple
metastases were selected. Radiotherapy was prescribed
according to simultaneous integrated boost technique
with all targets irradiated simultaneously over 10 daily
fractions. Doses of 30 Gy and 50Gy were prescribed to
PTV whole-brain and PTVmets , respectively. Bilateral
hippocampi were delineated according to RTOG 0933 trial
suggestions, on T1w MRI co-registered planning CT.
Clinical standard plans (s-IMRT) were compared with plans
aiming to spare hippocampus irradiation. Two plans were
re-optimized for hippocampal sparing using two Elekta
MLCs: MLCi2 with 10mm leaf width (hs10-IMRT) and Agility
with 5 mm leaf widths (hs5-IMRT). All plans were
evaluated using target coverage metrics, homogeneity
index (HI) and conformity index (CI). Normal tissue
complication probabilities (NTCP) for neurocognitive
function impairment (NCF) were calculated using a
predictive model developed by Gondi et al.
Results
Plans aiming to hippocampus sparing demonstrated
comparable planning target volumes coverage and no
differences in sparing of other organs at risk (brainstem,
optic chiasm, eyes, lens). Significant reductions in
hippocampal doses relative to standard plans were
achieved in all patients. Mean dose to bilateral
hippocampi was reduced from 36.5 Gy (range: 34.7-37.7
Gy) to 17.4 Gy (range: 11.2-24.7 Gy) and 16.4 Gy (range:
11.0-24.1) for hs10-IMRT and hs5-IMRT plans, respectively.
D40% was reduced from 36.9 Gy (range: 35.3-37.7 Gy) to
18.2 Gy (range: 11.8-25.2 Gy) and 17.2 Gy (range: 11.5-
25.0 Gy) for hs10-IMRT and hs5-IMRT plans, respectively.
Mean NTCP values for NCF impairment as predicted by
Gondi model decreased from 98.0% (range: 97.7-98.5%) to
62.1% (range: 34.8-83.9%) and to 58.2% (range: 33.4-
83.5%) for hs10-IMRT and hs5-IMRT plans, respectively.
Dose reductions depended mainly on metastases location
and distance from hippocampus.
Conclusion
IMRT plans aiming at sparing bilateral hippocampi can be
successfully optimized with SIB-IMRT despite the high-
dose irradiation of multiple brain metastases, providing a
significant reduction in NTCP for radiation induced NCF
decline.
EP-1578 Frameless intracranial radiosurgery with
Helical Tomotherapy: preliminary results.
M. Iacco1, C. Zucchetti1, M. Lupattelli2, C. Aristei2, C.
Fulcheri1, R. Tarducci1
1Santa Maria della Misericordia Hospital, Medical Physics
Department, Perugia, Italy
2Santa Maria della Misericordia Hospital, Radiation
Oncology Department, Perugia, Italy
Purpose or Objective
To report the preliminary results of radiosurgery
treatments with Helical Tomotherapy (HT) by means of an
non-invasive frame.
Material and Methods
Between April and October 2016, 6 patients underwent
radiosurgery with HT for treatment of 10 brain lesions with
a median dose prescription of 20 Gy (range 15-22 Gy). The
planning target volume (PTV) was created expanding 2mm
in all directions the gross tumor volume (GTV). The
median PTV was 1.5cc (range 0.6-7.7cc). Treatment plans
were performed with the following parameters: field
width of 1.05cm, pitch in the range 0.108-0.150, and
modulation factor (MF) in the range 1.5-3.5, leading to a
final MF of 1.6 on average (range 1.1-2.2). All plans were
prescribed according to ICRU83 at the median of PTV,
trying to limiting cold (D98%>95%) and hot spots (D2%<107%).
In addition, 12Gy-volumes (V12Gy ) of the healthy brain,
associated with symptomatic radiation risk of necrosis,
was reduced below 10cc. Treatment plans were analyzed
recording D98%, Dmean and D2% of the PTV. Moreover the
conformity, homogeneity and gradient score indexes were
calculated and compared with published reports of HT
radiosurgery. Furthermore, the V 12Gy of the healthy brain
was also evaluated. A mask-based fixation system has
been chosen, because of its high intracranial repositioning