ESTRO 38 Abstract book

S380 ESTRO 38

(22%) were dead and 105 patients (78%) were alive. No detrimental effect on neurocognitive functions was recorded. Grade II radionecrosis occurred in 13% of patients and grade III 6% of cases treated. Conclusion Fractionated SRS after surgical resection is a safe and feasible option in patients with large brain metastases and oligometastatic disease. PO-0741 Active spot-scanning proton therapy for intracranial meningiomas: CNAO experience E. D'Ippolito 1 , A. Iannalfi 1 , M. Bonora 1 , B. Vischioni 1 , M.R. Fiore 1 , S. Ronchi 1 , V. Vitolo 1 , A. Barcellini 1 , R. Petrucci 1 , A. Mirandola 1 , D. Maestri 1 , G. Magro 1 , A. Facoetti 1 , G. Viselner 2 , M. Ciocca 1 , L. Preda 2 , F. Valvo 1 , R. Orecchia 1,3 1 National Center of Oncological Hadrontherapy, Radiotherapy Unit, Pavia, Italy ; 2 National Center of Oncological Hadrontherapy, Diagnostic Imaging Unit, Pavia, Italy ; 3 European Institute of Oncology, Radiation therapy Unit, Milan, Italy Purpose or Objective Meningiomas are the most common primary intracranial tumors. If therapy is necessary, the standard treatment is gross total surgical resection. Proton therapy (PT) is an alternative therapeutic option for unresectable meningiomas, mostly located in the skull-base that are difficult to access, and a complementary treatment for complex and irregular tumors and lesions located in close proximity of critical organs at risk (OAR) as optic-pathways and brainstem where only subtotal or partial resection is possible. Aim of the study was to evaluate treatment results and toxicity in patients (pts) with meningiomas treated with active spot-scanning PT Material and Methods 79 pts (29 men and 50 women) with a median age of 54 years (range 15-85) with intracranial meningioma (histologically proven 50/79) were treated with PT between October 2012 to December 2017 at CNAO. Pts, tumor and treatment characteristics were summarized in Tab 1. 59 pts had skull-base lesions. 44 pts were treated as primary treatment (exclusively PT= 32 pts, postoperative PT = 12 pts), 35 pts were treated for recurrence after surgery. For pts with histological diagnosis, 33 pts had a diagnosis of World Health Organization (WHO) Grade I, 13 of WHO Grade II and 4 of WHO Grade III respectively, while 29 pts had radiological diagnosis (28/29 skull-base lesions) and in all these cases 68 Ga-DOTATOC-PET was performed before treatment. All pts were treated using pencil-beam active scanning PT. The median administered dose was 55.8 Gy (relative biological effectiveness -RBE) (range, 50.4- 66) at 1.8-2.0 Gy RBE per fraction. Gross tumor volume (GTV) ranged from 2.3-205.71 cm 3 (median 22.8, mean 36.5). Late toxicity was assessed according to Common Terminology Criteria for Adverse Events –CTCAE- V4.03 scale

or 2. No grade 3 or 4 acute toxicity was observed. Follow- up time was 38 – 75 months (median 58 months). To assess the results, MRI was performed every 6 months in the first two years of follow-up, then every 12 months. Partial tumor regression was observed in 28 patients (17.8%). In majority of patients (77.1%) the presence of a stable mass was confirmed. In 8 patients (5.1%) MRI scans revealed tumor progression (all of them underwent re-irradiation). None of the patients showed any severe neurological toxicity during follow-up. Most importantly, in patients with tumors located close to visual pathway, no visual impairment or loss of visual field was observed. Conclusion With the use of relatively low total dose we managed to achieve and maintain local control in 94.9% of patients and reduce the risk of CNS toxicity. Furthermore, it also allowed us to use re-irradiation in patients with tumor progression. PO-0740 Can HSRS on tumor bed replace WBRT in resected brain metastases? Results of a phase II study P. Navarria 1 , E. Clerici 1 , C. Franzese 1 , G.R. D'Agostino 1 , T. Comito 1 , F. De Rose 1 , D. Franceschini 1 , C. Iftode 1 , A. Tozzi 1 , F. Pessina 2 , L. Bello 2 , S. Cozzi 1 , I. Renna 1 , L. Di Brina 1 , M. Scorsetti 1 1 Humanitas Clinical and Research Hospital, Radiotherapy and Radiosurgery, Rozzano Milan, Italy ; 2 Humanitas Clinical and Research Hospital, Neurosurgery, Rozzano Milan, Italy Purpose or Objective The local control of large brain metastases is a crucial issue. Treatment options include whole-brain irradiation (WBRT), surgery, and stereotactic radiosurgery (SRS). As single-modality, none of these treatments are effective in controlling large brain metastases and a combined treatment is recommended. Surgery followed by WBRT was the standard treatment but it is burdened by a high risk of decline in neurocognitive functions. More recently surgery followed by SRS on the tumor bed is under investigation, but results are still poor. Based on this background we designed a prospective phase II study aimed to assess the benefit of surgical resection followed by hypofractionated radiosurgery (FSRS) on the tumor bed, instead of postoperative WBRT, for patient with single large brain metastases from solid tumor. Primary endpoint was local control rate; secondary endpoints toxicity, brain distant failure, and patients overall survival. Material and Methods Adults patients with primary diagnosis of solid tumors, KPS ≥70, controlled extracranial disease, single brain metastasis ≥ 2.1 , or smaller but conditioning mass effect and/or neurological deficits and/or massive aedema, and estimated survival ≥ 3 months were enrolled. Patients underwent previous WBRT were excluded. Surgical resection was performed with the aim to maximally (>95%) remove the tumor. Within 1 month from surgery, a fractionated SRS was performed on the tumor bed for a total dose delivered of 30 Gy in 3 daily fractions. Response was assessed according to RANO criteria, and toxicity using CTCAE scale. Incidence of radionecrosis was evaluated employing perfusion MRI and neurocognitive function with Milano Biccoca battery. Results Between 2014 and September 2018, 135 patients were enrolled, 63 female and 72 male with a median age of 49 years. The most common primary tumor was Non-Small Cell Lung Cancer (47%), followed by breast cancer (27%) and melanoma (10%). The median follow-up was 25 months (range 7-52 months). The 1,2-year LC rate were 98%, and 98%. Forty-two (34%) patients had new BDP at a median time of 19 months. The median 1,2-year overall survival were 24 months, 91.3% and 73%. At the last observation time, 30 patients