ESTRO 36 Abstract Book

284 / 1096

S271 ESTRO 36
_______________________________________________________________________________________________
70.2% infratentorial, the tumor grade was anaplastic in
62.0%, the extent of resection was complete in 85.1% and
64.5% of patients received a dose >54 Gy. The median
PRTV was 43.8 cc (1.1-287.9), and the median CEPTV was
13.3 cc (0-71.4). The median PRTVF was 49.4 cc (0-336.7)
and the median POTVF was 4.6 cc (0-118.7). A statistically
significant benefit in survival was seen with a POTVF equal
to 0 cc in univariate analysis for the DFS and the OS (71.9%
versus 40.3% p=0.006) and (93.7% versus 72.37% p=0.023)
respectively. In multivariate analysis, POTVF was also
statistically significant for OS (p=0.05) and almost
significant for DFS (p=0.06).
Conclusion
In this retrospective study, POTVF was found to be
significant predictor of overall survival after ependymoma
radiotherapy. POTVF was the more significant predictor of
survival compared with PRTV, suggesting that this volume
and residual contrast-enhancing tumor may be a more
accurate and meaningful reflection of the pathobiology of
ependymoma.
OC-0513 Radiation necrosis following stereotactic RT
and immunotherapy for melanoma brain metastases
O. Kaidar-Person1, T. Zagar 1, A. Deal2, S. Moschos3, M.
Ewend 4, D. Sasaki-Adams4, C. Lee3, F. Collichio3, D.
Fried1, L. Marks1, B. Chera 1
1 University of North Carolina- Chapel Hill- North
Carolina- USA-, Department of Radiation Oncology,
Chapel Hill, USA
2 UNC Lineberger Comprehensive Cancer Center- Chapel
Hill- North Carolina- USA, Statistics, Chapel Hill, USA
3 University of North Carolina- Chapel Hill, Medicine,
Chapel Hill, USA
4 University of North Carolina- Chapel Hill, Neurosurgery,
Chapel Hill, USA
Purpose or Objective
Stereotactic radiotherapy (SRT) is the standard treatment
for patients with limited number of brain metastases. In
the past few years, newer immunotherapies (immune
checkpoint inhibitors) have been proven to prolong
survival in patients with metastatic melanoma. The safety
of the combination of SRT and immunotherapy for brain
metastases is unknown.
Material and Methods
We retrospectively identified patients with melanoma
brain metastases treated with SRT between 2007 and
2015. Patients who did not have at least 3 months of
follow-up with imaging after SRT were excluded from the
analysis. Outcomes were compared between patients who
were treated with or without immunotherapy.
Results
A total of 58 patients were included, of these 29 were
treated with SRT and immunotherapy. MAPK inhibitors
(BRAF, MEK inhibitors) were used more often in the
immunotherapy group (9 vs. 2 patients). There was a
higher incidence of intracranial complications in patients
treated with immunotherapy and SRT. Eight patients had
radiation necrosis, all occurred in patients who were
treated with immunotherapy. Nine patients had
hemorrhage, of which 7 occurred in patients who were
treated with immunotherapy (p=0.08). However, patients
treated with immunotherapy and SRT had a significant
overall survival advantage compared to SRT without
immunotherapy (15 vs. 6 months, p = 0.0013).
Conclusion
Patients treated with SRT and immunotherapy, have a
higher incidence/risk of intracranial complications but a
longer overall survival.
OC-0514 radiation necrosis after proton beam therapy
- when and where does it happen?
S. Harrabi1,2,3, C. Gudden1, S. Adeberg1,2,3, N. Bougatf2,3,
T. Haberer3, S. Rieken1,2 , J. Debus1,2,3, K. Herfarth1,2,3
1 University Hospital Heidelberg, Radiation Oncology,
Heidelberg, Germany
2Heidelberg Institute of Radiation Oncology, HIRO,
Heidelberg, Germany
3Heidelberg Ion-Beam Therapy Center, HIT, Heidelberg,
Germany
Purpose or Objective
Radiation necrosis after irradiation of central nervous
system tumors is a rare but severe side effect. The
differentiation on magnetic resonance imaging between
postoperative changes, gliosis and therapy associated
changes remains a challenge and is not always possible
with absolute certainty. Available data almost exclusively
refer to conventional radiotherapy with photons (XRT).
Since the use of proton beam therapy (PRT) is constantly
increasing – especially for the treatment of neurooncologic
diseases – we set out to determine the safety of proton
irradiation by evaluating the incidence of radiation
necrosis.
Material and Methods
We reviewed 430 patients with a median age of 37 years
(4 – 85 years) who received radiotherapy between 2009
and 2015 for meningioma or low grade glioma with either
protons (n=276) or photons (n=154). Median applied dose
was 54 Gy (50 – 60 Gy). Clinical and radiological
information of regular follow-up examinations were
analyzed resulting in nearly 3.000 available magnetic
resonance imaging (MRI) examinations with a minimum
follow up of 12 months (median 30 months, range 12 – 82
months). Findings on MRI were delineated in the
treatment plan system and correlated with parameters of
the treatment plan. Complementary calculations for dose
distribution, linear energy transfer (LET) and relative
biological effectiveness (RBE) for the original treatment
plan using different models (Monte Carlo, Wedenberg,
Carabe) were made.
Results
The cumulative incidence of radiation necrosis after PRT
in our cohort was 3.3 % with a median time to occurrence
of 12 months (6 – 32 months). No risk factor could be
identified with regard to treatment specific parameters
such as optimization algorithm (single beam optimization
vs intensity modulated proton therapy), number of used
beams (one vs multiple), concomitant chemotherapy or
applied dose (≤54 GyE vs >54 GyE). However, the observed
radiation necrosis affected significantly often the
periventricular border and were almost exclusively at the
distal edge of the spread-out Bragg peak (SOBP).
Conclusion
Radiation necrosis after PRT can be a severe side effect
but is as rare as after XRT. The accumulation of incidence
at the distal edge of the SOBP and at the periventricular
border warrants further radiobiological investigation.
OC-0515 Radiation necrosis in children with brain
tumours treated with pencil beam scanning proton
therapy
B. Bojaxhiu 1, F. Ahlhelm2, M. Walser1, L. Placidi1, U.
Kliebsch1, L. Mikroutsikos1, P. Morach 1, A. Bolsi1, T.
Lomax1, R. Schneider1, D.C. Weber1
1Paul Scherrer Institute, Center for Proton Therapy,
Villigen, Switzerland
2Cantonal Hospital Baden, Department of Radiology,
Baden, Switzerland
Purpose or Objective
To assess the rate of radiation-induced brain necrosis (RN)
and related neurologic symptoms in paediatric patients
with primary brain tumours treated with Pencil Beam
Scanning (PBS) proton therapy (PT) with or without
concomitant chemotherapy at the Paul Scherrer Institute,
Switzerland.
Material and Methods
One hundred and seventy-one children and adolescent
young adults (AYA) (<18 years) with brain tumours were