Abstract Book

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ESTRO 37

Results 192 childhood leukemia survivors were included in this study, 86 in the screening group, 106 unscreened. Median time from RT to first screening MRI was 25 years (range 11-40 years) and the median number of screening MRIs was 1 (range 1-3). Screening MRI detected meningioma in 15 (17%) screened survivors. In the unscreened group, 17 (16%) had neurologic symptoms leading to an MRI; 9 patients (8.5%) were diagnosed with meningioma. The cumulative incidence of meningioma 25 years after CRT were 6.3% and 3.4% in the screened and unscreened groups respectively (p= 0.09). There were no significant differences in age of detection, tumour size, multifoca- lity, extent of resection, number of atypical and anaplastic histology, or use of adjuvant radiotherapy between screened and unscreened groups. There were 3 patients who had neurologic residual deficits in the unscreened group versus none in among screened patients, but this did not reach statistical significance (p= 0.25). Based on our results, a study of >600 survivors would be required to demonstrate clinically and statistically significant improved outcomes with Screening MRI was able to detect meningioma before becoming clinically apparent. However, we could not demonstrate a significant improvement in the likelihood of total resection or a decrease in morbidity. A larger sample could clarify potential reduction in neurologic sequelae associated with screening. OC-0591 Phase III randomized trial comparing two modalities of RS for brain metastases: Gammaknife vs Linac V. Palumbo 1 , P. Navarria 1 , S. Tomatis 1 , E. Clerici 1 , G.A. Carta 1 , P. Picozzi 1 , P. Mancosu 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy, Rozzano Milan, Italy Purpose or Objective Radiosurgery is a therapeutic approach for the treatment of brain metastases (BMs). Different technological moda- lities have been used. We draw this phase III trial with the aim to evaluate incidence of symptomatic radio- necrosis using gammaknife versus linac-based (EDGE) radiosurgery. Local control and overall survival (OS) were assessed. Material and Methods Patients with up to 4 BMs were enrolled. Inclusion criteria were: KPS ≥70, RPA class I-II, BMs maximum diameter ≤3 cm and/or with a total tumor volume <30 cm 3 . Prescribed dose was 24 Gy or 20 Gy depending on lesion dimension. Clinical outcome was evaluated by neurological examination and MRI. Results From October 2014 to August 2017, 134 patients of the expected 250, for 236 BMs were evaluated. Most common primary was NSCLC (53.7%). Symptomatic radionecrosis was observed in a total of 23 (9.7%) cases of the entire cohort evaluated. In the gammaknife ARM Grade II radionecrosis was recorded in 8 cases and Grade III in 3. In the EDGE ARM only grade II radionecrosis occurred in 12 cases treated. Five local progressions in site of SRS occurred. The median, 6 months- and 1 year- brain distant failure (BDF) were 22.4 months, 11% and 31%, respectively. Median progression free survival (PFS) was 8.7 months, 6- and 12 months PFS were 67.1% and 34.7%. The median, 6 months and 1 year OS were 17 months, 89.3% and 73.3%, comparable in both arms. In univariate and multivariate analysis the volume of BMs influenced radionecrosis rate. Conclusion Gamma-knife and LINAC based SRS for BMs were comparable in terms of LC. In this preliminary evaluation the risk of G3 radionecrosis was greater and earlier in the screening. Conclusion

gammaknife arm.

OC-0592 Hypofractionated stereotactic radiotherapy of large brain metastases: analysis of 350 patients P. Ivanov 1,2 , I. Zubatkina 1 , A. Kuzmin 1 , D. Nikitin 1 , V. Krasnyuk 1 , G. Andreev 1 , F. Schepinov 1 1 Radiosurgery- Stereotactic Radiotherapy and General Oncology clinic MIBS, Radiosurgery, Saint-Petersburg, Russian Federation 2 Polenov Russian Scientific Research Institute of Neurosurgery- Branch of Federal Almazov North-West Medical Research Centre, Neurooncology, Saint- Petersburg, Russian Federation Purpose or Objective To analyze radiological and survival outcomes in a large cohort of patients with brain metastases who received hypofractionated stereotactic radiotherapy (HSR) with a focus on short-term and long-term tumor response, complications and mortality. Material and Methods Patients with large brain metastases who underwent HSR between 2010 and 2016 were included in the study. Radiation treatments were performed with Gamma Knife 4C and Perfexion (Elekta AB, Stockholm, Sweden), Cyber Knife (Accuray, Sunnyvale, CA, USA) and linear accelerator TrueBeam STX (Varian Medical Systems, Palo Alto, CA). The median tumor volume was 23.5 cm 3 (from 9.1 to 106.7 cm 3 ). The number of metastases treated with HSR per patient varied from 1 to 6 with a mean of 2. Patients with multiple brain metastases were subjected to a combination of HSR and stereotactic radiosurgery (SRS). A three-fraction stereotactic radiotherapy was applied for irradiation of large brain metastases with the total prescription dose from 24 to 30 Gy at a median of 80% isodose. Radiation schemes were selected depending on the number of metastases, size, location, proximity to critical brain structures, histological type of primary cancer and patient general condition. Following treatment the patients underwent control MRI examination with standard protocols (2 mm T2 and 1 mm T1 with double contrast enhancement) at 8 weeks and then every 3 months. The median follow-up time after HSR was 9 months. Results The study revealed that the application of HSR for the treatment of large volume brain metastases provided a high level of local control (12-month local control rate was 86 %). Shrinkage of tumor volume by more than 50% was observed in a vast majority of patients with radiosensitive tumor histology, which resulted in considerable improvement of the patients’ neurological condition. Complications in the form of radiation necrosis occurred in 20% of patients at a median of 7.6 months after HSR. History of previous brain irradiation increased the risk of radiation necrosis (HR=2.8, p=0.002). For the entire cohort 12-month and 24-month overall survival rates after HSR were 45% and 24% respectively. There was no statistically significant difference in the median survival of the patients receiving HSR alone and those receiving HSR plus SRS. Mortality within 2 months after HSR was 9% and was associated with neurological deterioration or systemic disease progression. The best survival results were obtained in patients belonging to the first RPA-class who achieved one-year survival in 73% of the cases. Conclusion HSR and its combination with SRS is an effective treatment strategy for patients with brain metastases having at least one large unresectable lesion or a relatively large lesion located in/near critical brain structures.