1. Case studies: VMAT and SIB (simultaneous integrated boost) in pediatric tumours, from clinical target definition to toxicity as treated in the Radiation Oncology Department in Bank of Cyprus Oncology Center.
Marilena Theodorou, MD 1, , Andriana Peratikou, MSc, DABR, 2 , Stefani Stefanou MSc,CSci, MIPEM, 2, , Lora Ioannou, MSc, CSci, MIPEM, 2,, Efthymiou Themos MSc, 2, Erato Stylianou MSc, 2,,Ali Vehbi Artikan MSc, DABR, Aristotelis Giannos MSc 2, Kyriaki Michailidou, PhD, 4 Demetrios Andreopoulos, MD,PhD 1
1 Radiation Oncology Department, Bank of Cyprus Oncology Center, 2 Medical Physics Department, Bank of Cyprus Oncology Center, 3 Department of electron microscopy/molecular pathology and the Cyprus School of molecular medicine, the Cyprus Institute for Genetics and Neurology
Contact:
Radiation Oncology and Radiodiagnostics, Bank of Cyprus Oncology Center, Nicosia, Cyprus ,
Introduction
A. 10 year old boy with a Medulloblastoma WHO IV after total resection with a KI=70% due to astathia and diplopia, referred for irradiation of the neuroaxis and boost to the tumor bed with concurrent chemotherapy (Vincristin), according to Medulloblastoma protocol.
B. 3,5 year old boy with a Wilms tumor right ca. 12cm after neoadjuvant chemotherapy (Vincristin, Actinomycin C, Doxorubicin) and operation referred for adjuvant radiation (abdominal bath radiation) according to the SIOP Wilms tumor protocol. .
Methods
A. Radiation Neuroaxis
Phase I Neuroaxis RT 23,4 Gy in13# (1,8Gy/#). Technique used: VMAT partial rapid arc with 3 isocentres
 Phase II Boost Primary Tumor Bed IV Ventricle cumulative to 54 Gy (1,8Gy/#)
 Contouring
 Phased I+II
Fusion of pre-OP-MRI and post-OP-MRI with Planning CT with contrast, no tumorrest in Planning CT with contrast
GTV=macroscopic tumor pre-OP
CTV= OP-cavity
PTV-Boost = CTV/GTV+1cm SS adapted in brainstemm
 Contouring for Neuroaxis (as per Tomotherapy Richtlinie)
CTV1=Brain (up to Foramen magnum)
PTV1=CTV1+1cm SS, caudal 2cm
CTV2= cervical spine
PTV2=CTV2+1cm SS
CTV3=thoracic spine
PTV3=CTV3+1cm cranial/caudal, 1,5 cm lateral
CTV4=lumbar-sacral -spine
PTV4=CTV4+1cm cranial/caudal, 2cm lateral
 PTV=Sum-PTVs(PTV1,2,3,4)
B. Radiation Abdominal Bath
Phase I
Abdominal Bath Radiation, total dose 12 ,6 Gy in 7# (1, 8 Gy/#) (PTV=abdominal bath inclusive peritoneum, retroperitoneum and pelvis), SIB Boost 14 Gy in 7# (2Gy/#)
Phase II
Boost primary tumor bed right retroperitoneum and kidney, LN iliaca (R1 resected, metastatic LN) 10Gy in 5# (2Gy/#), cumulative 24Gy. Constrain for the contralateral kidney with Dmax 12Gy according to protocol
Clinical target Definition
Fusion of pre-OP-MRI and post-OP MRI with Planning CT with contrast
GTV1= pre-OP tumor right kidney
CTV1=tumorbed, iliaca LN clips
PTV1=CTV+1cm
SIB Boost= CTV1+1cm
PTV=abdomen
Results
The coverage of the PTVs and SIB Boost ranged from 97% to 100% and the organs at risk were spared and within tolerance. Special attention was given to the dose received by the contralateral kidney and the liver as per the abdominal bath irradiation for Wilms tumors protocol. Both children tolerated the treatment well without significant side effects or complications except for fatigue and alopecia for the boy with neuroaxisradiation. To prevent radiation induced gastrointestinal symptoms, prophylactic Dexamethasone and antiemetics were prescribed. The further FUs gave no late side effects. B
Example A: VMAT plan, 23,4Gy/13# to the neuroaxis, boost tumor bed 54Gy, partial rapid arc to avoid radiation of both arms
Example B:
Phase I
Abdominal Bath Radiation: total dose 12 ,6Gy (1, 8 Gy/#) (PTV=abdominal bath including peritoneum, retroperitoneum and pelvis), SIB Boost Gy (2Gy/#)
Phase II Boost primary tumor bed right retroperitoneum and kidney, LN iliaca (R1 resected, metastatic LN) 10Gy (2Gy/#) cumulative 24Gy
Conclusion and summary
In conclusion it is recommended that VMAT technique is used for pediatric tumors due to the improved coverage of the targets and lower toxicity for the OARs with reduced side effects. The shorter radiation time, especially in treatments of young children is of great benefit in order to avoid sedation.
DEGRO 2018, Leipzig