ESTRO 38 Abstract book

S870 ESTRO 38

range: 23.4 to 39.0 Gy) ± boost, and 3/19 with IFRT (dose range: 21.0 to 54.0 Gy) ± boost. All patients with central and peripheral hypothyroidism underwent CSRT (dose range: 23.40 to 39.0 Gy) ± boost. Three of 6 patients with fT4 deficiency were treated with CSRT (dose range: 23.40 to 36.00 Gy) ± boost, 3/12 with IFRT (dose range: 50.40 to 60, 00 Gy) ± boost. Conclusion Our data confirm the frequency of hypothyroidism post-RT in pediatric patients; the relationship between dose to pituitary gland and to thyroid and damage is ongoing. EP-1613 A dosimetric comparison of Proton and VMAT for Pediatric Ewing sarcoma of pelvis and spine F. Meniai-Merzouki 1,2 , M. Vigan 3 , F. Goudjil 4 , S. Helfre 1,2 1 institut curie, Radiation oncology Department, Paris, France ; 2 centre de protontherapie, Radiation oncology Department, Orsay, France ; 3 Biostatistic Department, , France ; 4 Physics department, Orsay, France Purpose or Objective To compare the dosimetric results of proton radiation with volumetric modulated arc therapy (VMAT) for pediatric Ewing Sarcoma of pelvis and spine. The goal was ti assess the potential advantage of proton over VMAT palnning in pelvis and spine Ewing's sarcoma. Material and Methods Ten patients with Ewing sarcoma of the pelvis and spine treated with proton beam at Protontherapy center (CPO) at Institut Curie. VMAT plans had generated and analyzed. To facilitate dosimetric comparisons, clinical target volumes and normal tissus volumes were held constant. Plans were optimized for target volume coverage and normal tissus sparing. Results The average dose coverage values for CTV were comparable in PROTON and VMAT plans. Whereas the Proton plans achieved a higher conformity index compared to the VMAT plans (conformity index 1.2±0.2 vs.1, p=0.009), The index of homogenity (IH) did not differ significantly. For the bladder, Kidney, head femoral and testis Dmean were significantly reduced in Proton plans. For the bowel and rectum, there was no significant difference in Dmean.The volume of normal tissue receiving at least 5 Gy (V5) was significantly higher in VMAT plans compared with Proton, whereas at high dose levels (V30) it was significantly lower. Conclusion Compared to VMAT, Proton showed significantly better results regarding dose conformity (p=0.009) and mean Dose of bladder (p=0,004), kidney (p= 0,01).Proton delivered a lower healthy tissue dose than VMAT.Thus, dose escalation in the radiotherapy of pelvic and spine Ewing’s sarcoma can be more easily achieved using proton. EP-1614 Incidence of second malignancies among pediatric patients treated with helical Tomotherapy E. Coassin 1 , A. Drigo 2 , L. Barresi 2 , G. Fanetti 3 , C. Elia 1 , G. Sartor 2 , G. Franchin 3 , M. Mascarin 1 1 IRCCS Centro di Riferimento Oncologico CRO di Aviano, Pediatric Radiotherapy and AYA Unit, Aviano, Italy ; 2 IRCCS Centro di Riferimento Oncologico CRO di Aviano, Medical Physics, Aviano, Italy ; 3 IRCCS Centro di Riferimento Oncologico CRO di Aviano, Radiation Oncology, Aviano, Italy Purpose or Objective Intensity modulated radiation therapy (IMRT) delivered with helical Tomotherapy (HT) has been increasingly applied in young patients with cancer. Concerns about a potential increase of radiation-induced malignancies (SMN) exist. The purpose of this study was to determine the incidence of SMN among pediatric patients treated with HT.

Material and Methods We performed a retrospective study of 146 patients less than 24 years of age treated with HT since its introduction in 2006 to September 2013 at Centro di Riferimento Oncologico CRO in Aviano, Italy. The main outcome measure was the incidence of SMN after radiation. Results Seventy-eight patients with a follow-up of at least 5 years after the end of radiotherapy were included in the analysis. The median follow-up was 7.6 years (range, 5- 12.2). Forty-seven and 14 patients were followed for at least 7 and 10 years, respectively. The median age at treatment was 13.5 years (range, 1.5-24). Forty-five patients were males and 33 were females. Patients were irradiated with HT alone or in combination with other radiation techniques for CNS tumors (n=33), lymphomas (n=21), sarcomas (n=17), H&N carcinomas (n=4), or other hystologies (n=3). Treatment sites were brain (n=21, 2 whole ventricular), mediastinum (n=20), craniospinal (n=12), H&N (n=6), pelvis (n=6), thorax (n=5, 2 total pleural), limbs (n=4), abdomen (n=3, 1 whole abdomen), spine (n=1). Median prescribed doses were 54 Gy (range, 8-59.4) for CNS tumors, 25.2 Gy (range, 9-50) for lymphomas, 50.4 Gy (range, 41.4-66) for sarcomas, 66 Gy (range, 63-70) for H&N carcinomas, and 15-21 Gy for the remaining cases. At a median follow-up of 7.3 years (range, 5-12.2), 57 patients (73%) were alive in complete remission. Among these long-term survivors, a 17.5-year- old female affected by Hodgkin lymphoma developed a recurrent fibromatosis of the soft tissues of the breast region close to the central venous catheter insertion site within the irradiated area 5 years after HT (prescribed dose, 14.4 Gy in 8 fractions). At a median follow-up of 7.2 years (range, 5-8.9), 10 patients (13%) were died of disease. One patient died because of esophageal cancer 7 years after total pleural irradiation delivered for an Ewing sarcoma of the right thoracic wall (prescribed dose, 36 Gy in 20 fractions). The tumor arose in the high-dose radiation volume and was considered a SMN. No other SMN occurred. Eleven patients (14%) were alive with disease without evidence of SMN at the time of the study. A 6- year-old girl affected by Li-Fraumeni syndrome irradiated to a dose of 50.4 Gy in 28 fractions for an anaplastic rhabdomyosarcoma of the right masticator space was alive in first complete remission without SMN 9.6 years after HT. Conclusion At a median follow-up of more than 7 years, IMRT delivered with HT resulted not associated with an increased risk of SMN due to low-dose irradiation to normal tissues as previously reported. Longer follow-up is needed to confirm this finding. EP-1615 Impact of pretreatment imaging modality on the response to palliative radiation for bone metastases Y. Wada 1 , E. Okuyama 1 , S. Kumagai 1 , M. Sasajima 1 , T. Tozawa 1 , N. Takagi 1 , A. Anbai 1 , M. Hashimoto 1 1 Akita University Graduate School of Medicine, Radiology, Akita, Japan Purpose or Objective MRI, bone scintigraphy, and 2-deoxy-2-( 18 F)-fluoro-D- glucose positron emission tomography ( 18 FDG-PET) have been reported to be more sensitive than CT for detecting malignant bone lesions. Therefore, it was thought that gross tumor volume (GTV) contoured on MRI, bone scintigraphy, or 18 FDG-PET is more accurate than that on CT. The aim of the present study was to evaluate whether the imaging modality before irradiation affects the Electronic Poster: Clinical track: Palliation