ESTRO 2020 Abstract book

S517 ESTRO 2020

Median follow-up after re-irradiation was 5 (2-20) months. SRT was delivered on a median number of 2 (1-21) lesions; 3 pts underwent SRT on > 5 lesions simultaneously (9, 19 and 21 lesions, respectively). Acute toxicity was G2 cefalea in 3 pts (GTV>1cc or >3 lesions), successful treated increasing the dose of corticosteroids. Radionecrosis occurred in only one patient (GTV>1cc, 2 previous VMAT SRT, prescribed dose 30 Gy in 5 fractions), symptomatic for seizures, treated with corticosteroids and levetiracetam. Local control, evaluated with MRI in 13 pts was: partial response in 8 pts, stable disease in 3, progressive disease in 2 patients. Nine pts presented intracranial disease progression (pts treated on >3 lesions). Eight pts were dead at the last follow up, 2 for systemic progression and 6 for intracranial progression. Six months and 1 year OS were 46% and 15% respectively. Conclusion SRT for re-irradiation is feasible, with only 1 case of radionecrosis registered, and effective, with SD or PR in the majority of patients. An accurate patient selection is warranted in order to avoid toxicity and a longer follow- up is needed to confirm the low radionecrosis rate. PO-0880 SRS in brain metastases from colorectal- cancer. A Radiation Oncology Italian Association study P. Navarria 1 , E. Clerici 2 , T. Comito 3 , S. Cozzi 4 , V. Pinzi 5 , P. Ciammella 6 , S. Scoccianti 7 , V. Borzillo 8 , P. Anselmo 9 , E. Maranzano 9 , V. Dell'acqua 10 , B. Jereczek-Fossa 11 , N. Giaj Levra 12 , G. Minniti 13 , A.M. Podlesko 14 , E. Giudice 15 , M. Buglione di Monale e Bastia 16 , S. Pedretti 16 , A. Bruni 17 , I. Bssi Zanetti 18 , S. Borgesi 19 , F. Busato 20 , M. Scorsetti 21 1 Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano Milan, Italy ; 2 Humanitas Cancer Center and Research Hospital, Radiotherapy and Radiosurgery Department, Rozzano- Milano, Italy ; 3 Humanitas Cancer Center and research hospital, Radiotherapy and radiosurgery department, Rozzano- Milan, Italy ; 4 Humanitas cancer center and research hospital, Radiotherapy and radiosurgery, Rozano- Milan, Italy ; 5 Istituto Neurologico Fondazione "Carlo Besta, Radiotherapy, Milan, Italy ; 6 Azienda Ospedaliera Arcispedale S Maria Nuova, Radiation Therapy Unit- Department of Oncology and Advanced Technology, Reggio Emilia, Italy ; 7 Azienda Ospedaliera Universitaria Careggi, Radiotherapy, Firenze, Italy ; 8 Istituto Nazionale per lo Studio e la Cura dei Tumori - Fondazione "Giovanni Pascale, radiotherapy, Napoli, Italy ; 9 S. Maria" Hospital, radiotherapy, Terni, Italy ; 10 IEO European Institute of Oncology - IRCCS, Raddiotherapy, Milan, Italy ; 11 IEO European Institute of Oncology - IRCCS, Radiotherapy, Milan, Italy ; 12 Sacro Cuore Don Calabria Hospital, Radiotherapy, Negrar- Verona, Italy ; 13 UPMC San Pietro FBF, Radiotherapy, Roma, Italy ; 14 ospedale di Perugia, radiotherapy, perugia, Italy ; 15 Policlinico Universitario Tor Vergata, Radiotherapy, Roma, Italy ; 16 University and Spedali Civili Hospital, radiotherapy, brescia, Italy ; 17 Ospedale di Modena, radiotherapy, Modena, Italy ; 18 CDI, Radiotherapy, Milan, Italy ; 19 ospedale di Arezzo Valdarno, radiotherapy, Arezzo, Italy ; 20 IOV, radiotherapy, Padova, Italy ; 21 humanitas cancer center and research hospital, radiotherapy and radiosurgery, rozzano- milan, Italy Purpose or Objective The prognosis of brain metastatic colorectal cancer patients(BMCRC) is poor. Several local treatments have been used, but the optimal treatment choice remains an unresolved issue. We evaluated the clinical outcomes of a large series of BMCRC patients treated in several Italian centers using stereotactic radiosurgery(SRS). Material and Methods One-hundred-eighty-five BMCRC patients for a total of 262 lesions treated were evaluated. Treatments included surgery followed by postoperative SRS to the resection cavity, and SRS, either single-fraction, then

was created in the same way as CTVb-Pre and CTVb-Mid, and PTVb-Post was created by adding a 5-mm margin to CTVb-Post. To investigate PTVb-Post coverage in the Pre- and Mid- boost plans, Post-MRI was fused with planning CT, and the dose-volume histograms of PTV-Post were compared. Additionally, the conformity indices (CIs) of the Pre-and Mid-boost plans were compared. CIs was defined as the ratio of the volume that received 95% of the prescribed dose to the PTV. Results In all patients, the median V95 values of PTVb-post of the Pre-boost plan (V95pre) and the Mid-boost plan (V95mid) were 95.6% and 98.3%, respectively, and the median V90pre and V90mid values were 97.9% and 99.6%, respectively (P<0.01 and P<0.01, respectively). The median V95pre and V95mid values of patients after gross total resection were 97.4% and 98.8%, respectively (P=0.46); in contrast, those of patients after partial resection or biopsy were 92.2% and 98.1%, respectively (P<0.01). In a similar fashion, V90pre was significantly lower than V90mid in patients after partial resection or biopsy. The median CIs of Pre-plan and Mid-plan in all patients were 1.44 and 1.47, respectively (P=0.31). The median CIs of Pre-plan and Mid-plan of 31 patients after gross total resection were 1.61 and 1.48, respectively (P=0.01); in contrast, those of the 31 patients after partial resection or biopsy were 1.36 and 1.44, respectively (P=0.19). Conclusion In postoperative irradiation of GBM, continuing treatment according to only the pre-irradiation MRI may result in decreased target volume coverage. ART can provide dosimetric benefit with mid-treatment re-planning. PO-0879 Stereotactic radiotherapy for re-irradiation of relapsed intracranic lesions R. Tummineri 1,2 , A. Fodor 1 , F. Borroni 1,2 , F. Zerbetto 1 , C.L. Deantoni 1 , A.M. Deli 1 , N. Slim 1 , M. Pasetti 1 , S. Broggi 3 , C. Fiorino 3 , N.G. Di Muzio 1,4 1 San Raffaele Scientific Institute, Department of Radiotherapy, Milano, Italy ; 2 Milano-Bicocca University, Department of Radiotherapy, Milano, Italy ; 3 San Raffaele Scientific Institute, Medical Physics, Milano, Italy ; 4 Vita-Salute San Raffaele University, Department of Medicine and Surgery, Milano, Italy Purpose or Objective Stereotactic Radiotherapy (SRT) is increasingly used for the treatment of patients (pts) with recurrent primary brain tumors or metastasis (mts) after previous radiotherapy (RT). We analyzed the outcomes in pts From 01/2018 to 09/2019, 72 intracranial lesions in 17 pts were treated with SRT Cyberknife® (Accuray, Sunnyvale, CA)(CK). Six pts presented recurrent mts from breast cancer, 7 pts from NSCLC, 2 patient glioblastoma (GBM) and 1 patient intracranial hemangiopericytoma (HPC). Previous RT on the same volume was performed with: Gamma Knife radiosurgery (GK) in 3 pts, VMAT SRT in 3 pts, CK in 5 pts, whole-brain RT (WBRT) in 5 pts, post-operative Tomotherapy on tumor bed in 1 patient, post-operative 3D-CRT on tumor bed in 2 patient. Median time from the last RT was 11 (2.73-40.5 months). Gross tumor volume (GTV) and planning target volume (PTV) were delineated by the fusion of CT and MRI in whole pts. Median GTV size was 0.18 (0,02-36,76) cc. PTV was obtained adding an expansion of 1 mm to GTV. Median PTV size was 0.44 (0,07- 60,96) cc. Median prescribed dose was 35 (24-35) Gy in 1- 5 fractions, at a median isodose of 79% (70-80%). Prophylactic corticosteroid therapy was prescribed to all pts and antiedema therapy with mannitol to 1 patient simultaneously treated on 21 lesions. Results treated in our Institute. Material and Methods