ESTRO 2020 Abstract book

S207 ESTRO 2020

Conclusion The 30 Gy in 10 fractions schedule seemed more effective in reducing BM, although no statistically significant interaction was observed, but the 15 fractions schedule was statistically significantly less toxic. This trade-off should be taken into account when considering PCI for NSCLC.

their initial symptoms, 94(61%) stable symptoms, and 27(18%) worsened their pre-treatment symptoms. Only in 2(1%) cases MRI showed progression of VS. Crude radiologic TC rate was 99%. TC was not conditioned by tumour volume, prescribed dose (≤14Gy vs >14Gy), Koos tumor class (I+II vs III+IV) and/or previous surgery. Among patients with “serviceable-hearing” (80-52%), 54(67%) maintained their functional hearing score, 15(19%) improved and 11(14%) worsened. Median tumor size in “serviceable-hearing” patients was 5mm (range, 0,2-30) and median dose administered was 14Gy (range, 12-17,5). No statistically significant difference was found with regard to tumor size (≤5mm vs>5mm) and prescribed dose (≥14 Gy vs<14 Gy).5 of 126(4%) patients without pre-SRS facial toxicity, developed incomplete facial nerve palsy, that regressed in a median time of 6 months. 15 of 144(10%) patients without pre-SRS trigeminal neuralgia developed trigeminal toxicity which was transient or stable/mild during follow-up in 13 (8.5%) patients. In only 2(1%) cases trigeminal toxicity was severe and appeared at a median time of 12 months. Late toxicity was significantly correlated to tumor size (≤5mm vs >5mm) (p=0.05). Prescribed dose and Koos tumor grade (I+II vs III+IV) not showed a statistically significant. Conclusion Our data confirm the feasibility of SRS in the treatment of VS also in patients with “serviceable hearing” with a high rate of hearing preservation. The present analysis of VS patients with a median FU of ≥ 6 years confirmed the excellent TC and low iatrogenic toxicity of both LB-SRS and CK-SRS. PH-0357 Proton therapy re-irradiation of intracranial meningiomas failing after previous radiation therapy. D. Amelio 1 , D. Scartoni 1 , S. Vennarini 1 , A. Turkaj 1 , I. Giacomelli 1 , M. Amichetti 1 1 Centro di Protonterapia, U.O. Protonterapia- Azienda Provinciale per i Servizi Sanitari - Trento, Trento, Italy Purpose or Objective Despite the favorable outcomes with local control rates of up to 90% after ten years, progression after radiotherapy (RT) of intracranial meningiomas (MS) does occur. In those cases, re-irradiation is often difficult due to the limited radiation tolerance of the surrounding tissue. Aim of this analysis is to report safety and efficacy of proton therapy (PT) for re-irradiation of recurrent MS Material and Methods Between March 2015 and June 2019, 25 patients (pts) with 29 intracranial MS were re-irradiated with PT at our institution. Location of the primary lesion was skull base (n = 21) and convexity (n = 8). All but two pts had histologically proven diagnosis of MS (80% were WHO grade II). Median age was 66 years (range, 38-83). Median Karnofsky Performance status was 80 (range, 70-100). All pts failed after previous RT: 33% after Gamma-knife, 43% after Cyber-Knife, 10% after Tomotherapy, 14% after Linac-based stereotactic radiotherapy. Median time from initial irradiation to re-irradiation was 36 months (range, 18-60). Treatment planning was based on morphological magnetic resonance imaging (MRI) with contrast enhancement medium administration. All pts received also 68-Ga-DOTATOC-PET to identify the so-called Biological Tumor Volume. Clinical target volume ranged from 7 to 176 cc. All but one pts (who received 60 Gy in 30 fractions) were treated with 54 GyRBE in 30 fractions. All the pts was treated with active beam scanning PT using 3-4 fields with single or multiple field optimization technique. Toxicity was assessed according to Common Terminology Criteria

PH-0356 Long-term results after radiosurgery (SRS) of vestibular schwannomas (VS). A retrospective analysis. P. Anselmo 1 , V. Pinzi 2 , S. Terenzi 1 , E. De Martin 2 , F. Trippa 1 , P. Gaviani 3 , M. Casale 1 , L. Fariselli 2 , E. Maranzano 1 1 Ospedale Santa Maria, Radiotherapy Oncology Centre, Terni, Italy ; 2 Fondazione IRCCS Istituto neurologico Carlo Besta, Department of Neurosurgery- Radiotherapy Unit, Milan, Italy ; 3 Fondazione IRCCS Istituto neurologico Carlo Besta, Clinic Neuro-Oncology Unit, Milan, Italy Purpose or Objective Patients with sporadic VS treated with a single dose of SRS with a minimum follow-up > 3years were retrospectively analysed to asses tumor control (TC) and SRS related toxicity. Material and Methods Patients received Linac-based (LB) SRS or Cyber-Knife (CK) SRS. Patients not able to discriminate words or not hearing at all, were scored as ‘non-serviceable hearing’. Trigeminal and facial nerve functions were assessed before and after treatment. Results Between 2002 and 2016, 153 VS were treated in 153 patients. 116(76%) VS received LB-SRS and 37(24%) CK-SRS. Male/female ratio was 70/83. Median age was 60y (range,20-84). Median prescribed dose was 14Gy (range, 12-20). Median tumor diameter was 5mm (range,0.2-23). SRS was performed as salvage therapy for recurrent or progressive tumors in 36(23%) patients already submitted to total or subtotal resection (10-28% and 26-72%, respectively). The other 117(77%) patients underwent SRS alone. 25(16%), 61(40%), 52(34%) and 15(10%) VS were classified as Koos tumor grade I, II, III and IV, respectively. 147(96%) patients had hearing loss as an initial symptom, of which 73 (48%) with “non-serviceable” hearing function. Trigeminal neuralgia and facial pain/paraesthesia were presenting symptoms in 9(6%) and 27(17%) patients, respectively. At a median follow-up of 6 years(range,3– 16), 32(21%)patients had an objective improvement of