ESTRO 2021 Abstract Book

S1181

ESTRO 2021

January 1998 and December 2017 were retrospectively evaluated. Results

Fifty-nine patients were evaluated with a median age of 5.48 years (range 1.03-22 years). Ependymal tumours were either supra-tentorial (n=17, 28.8%), infra-tentorial (n=37, 62.7%) or spinal (n=5, 8.5%). Surgical rates were: gross total resection (GTR) 67.8% (n=40), subtotal resection (STR) 28.8% (n=17), and biopsy 3.4% (n=2). Thirty-six patients (61%) received adjuvant radiotherapy (n=10 protons, n=26 photons), at a median age of 8.86 years (range 1.27-22.14 years), of whom 4 received chemotherapy prior to radiotherapy. Fourteen patients (23.7%) received chemotherapy as the sole adjuvant treatment at a median age of 1.7 years and 9 patients (15.3%) did not receive any adjuvant therapy. The median follow-up was 4.7 years (range 0.19-19.7 years); 42 patients (71%) experienced disease recurrence after a median of 1.32 years from diagnosis (range 0.08-19.5 years). The majority of first recurrences were local (n=26, 61.9%), while 12 patients (28.6%) had distant relapse and 4 patients (9.5%) had simultaneous local and distant relapse. The 5- and 10-year event- free survival (EFS) were 34.9% (95% CI 22.9 - 47.1%) and 27.8% (95% CI 15.4 - 41.6%), respectively. The 5 and 10-year overall survival (OS) were 67% (95% CI 52.6 - 77.9%) and 54.4% (95% CI 39.2 - 97.4%), respectively. Predictors of superior EFS were GTR (p=0.0037) and adjuvant radiotherapy (p=0.001), while predictors of superior OS were GTR (p=0.018) and older age (p=0.027). When analysed as a continuous variable, increasing age by 1 year reduced the risk of death by 9% (p=0.027). When analysed as a categorical variable, those aged >3 had better EFS compared to those aged ≤3 (HR 0.52, 95% CI 0.28 - 0.96, p=0.038). In recurrent cases, the 2- , 5- and 10-year EFS were 31% (95% CI 17.8 - 45%), 9.5% (95% CI 3 - 20.6%) and 4.8% (95% CI 0.9 - 14.2%), respectively. The 2-, 5- and 10-year OS were 78.3% (95% CI 62.4 - 88.1%), 54.2% (95% CI 37.3 - 68.4%) and 38.3% (95% CI 22.5 - 54%), respectively. At recurrence, superior OS was demonstrated for any surgical intervention (p=0.015), GTR (p=0.022), and radiotherapy treatment (p=0.004). Conclusion These results demonstrate the favourable prognostic impact of radiotherapy in paediatric ependymoma and provide further validation of the strong prognostic impact of GTR, both in the adjuvant and relapsed settings. Prospective studies are warranted to explore the role of radiotherapy in improving survival outcomes for patients ≤3 years old, a cohort with poor prognosis. PO-1439 Clinical results of SBRT for spinal metastases using dedicated contouring/planning system V. Figlia 1 , N. Giaj-Levra 1 , R. Mazzola 1 , M. Rigo 1 , F. Cuccia 1 , L. Nicosia 1 , F. Ricchetti 1 , G. Attinà 1 , E. Pastorello 1 , G. Sicignano 1 , A. De Simone 1 , S. Naccarato 1 , D. Gurrera 1 , R. Ruggieri 1 , F. Alongi 1,2 1 IRCCS Sacro Cuore Don Calabria Hospital, Cancer Care Center, Advanced Radiation Oncology Department, Negrar (Verona), Italy; 2 University of Brescia, Radiation Oncology Department, Brescia (Bs), Italy Purpose or Objective To report clinical results of spinal metastases SBRT using a dedicated software (Element Spine SRS®, Brainlab™). Materials and Methods The selection criteria were as follows: diagnosis of spinal metastases (n ≤ 3), life expectancy >3 months, controlled primary tumor. The dedicated software Elements Spine SRS® was used to co-register the MRI-T1 sequences or PET-CT scans for target volume and the organ at risks definition, using a dedicated anatomical atlas. Gross tumor volume (GTV) was defined as macroscopic lesion on T1-MRI or pathological uptake on PET- CT. Clinical target volume (CTV) was created by an expansion of the GTV according to international guidelines, including adjacent normal bone to avoid subclinical tumor spread. Planning target volume (PTV) was obtained by adding 1 mm isotropic margin to the CTV. Different dose prescription ranged between 10-24 Gy in 1-3 fractions (fx). Toxicity and tumor response were evaluated with periodic clinical evaluations and PET-CT or MRI scans, using CTCAE v5.0 scale for toxicity assessment, Kaplan-Meier method for survival endpoints and PET response criteria (PERCIST) or RECIST criteria v1.1 for tumor response evaluation. Results From April 2018 to December 2020, 118 spinal metastases in 85 patients (median age 66 years, range 43-85) were treated with Linac-based SBRT. The most common histologies were prostate in 58.8% and breast in 29.4% pts. The cervical spine was involved in 8.5% cases, thoracic spine in 58.5% and lumbar spine in 33% cases. The anatomical part of the vertebra affected was the vertebral body in 73 metastases (61.9%), peduncle in 10 (8.5%), spinal process in 5 (4.2%) and mixed vertebral sites in the residual 30 (25.4%) cases. A total dose of 12 Gy/1-2 fx was prescribed in 7 pts as re-irradiation, 18 Gy/3 fx in 19 lesions (16.1%), 21 Gy/3 fx in 54 (45.8%) and 24 Gy/3 fx in 38 lesions (32.2%). In 38 selected cases (radio-resistant histology and/or small GTV area) a simultaneous integrated boost to the GTV was proposed (range dose 24–27 Gy/3 fx). At a median follow-up of 10 months (range 3–31 months), local control rates at 6-months and 1-year were both 97.9%. No acute or chronic adverse events ≥3 grade were reported at the follow-up. At the time of the analysis, 97 lesions were evaluable for response by PET-CT scans: complete metabolic response was observed in 36 (37.1%) cases, partial response in 38 (39.2%), stable disease in 21 (21.6%) cases and only two cases of local progression was recorded at 6 months from SBRT. Conclusion Spine SBRT using this dedicated software is effective and well-tolerated, with high rate of early metabolic response. Longer follow-up is needed to assess late toxicity profile and outcomes. Digital Poster: Palliation

PO-1440 Radiotherapy for bone metastases in gynecologic malignancies. N. Bychkova 1 , E. Khmelevsky 2

1 P.A.Hertsen Moscow Oncology Research Institute – Branch of the National Medical Research Radiological Centre , Radiotherapy Department, Moscow, Russian Federation; 2 P.A.Hertsen Moscow Oncology Research Institute – Branch of the National Medical Research Radiological Centre, Radiotherapy Department, Moscow,