ESTRO 2020 Abstract book

S709 ESTRO 2020

Material and Methods Data of 95 consecutive patients (190 lesions treated) affected by brain metastases from breast cancer who underwent SBS with CyberKnife (Accuray, USA) from January 2012 to December 2017 were retrospectively analysed. Parameters included demographics, histology and primary tumour characteristics, presence and control of extracranial disease, number of lesions, single and total gross target volume (GTV). OS, LC and DBC at 3 years were evaluated. Results Total median SRS dose was 21 Gy (range, 15 -25 Gy) given in 1 to 5 fractions, in alternative days. After a median follow-up of 18 months (range 1-82), at least one radiological evaluation was available for 79 patients (156 lesions). LC was reported in 136 of 156 treated lesions (87%) while DBC was observed in 58 of 79 patients (26%). Thirty-four patients are still alive and 3-y OS was globally 31.5 %. Univariate analysis showed that the absence or controlled systemic disease at the time of SRS were associated better DBC (p = 0.013) and OS (p = <0.0001). The correlation between OS and controlled systemic disease was confirmed also by a multivariate analysis (p = 0.0003). In a multivariate analysis, older age ( > 60 years) and presence of 2-3 metastatic brain lesions were significantly negatively correlated to OS (p = 0.005 and 0.033, respectively). Single lesion GTV influenced LC, most of local recurrence occurred to lesions with GTV ≥ 0.80 cm3 (p = 0.005) while smaller lesions showed a 3-y LC > 92% . No patients in our series experienced severe neurotoxicity (Grade 4-5 in the Common Terminology Criteria for Adverse Events).

Conclusion SRS is safe and efficacious treatment for brain metastases from breast cancer. Local control reaches 90% at 3 years with predominant distant intracranial pattern of failures, especially for lesions < 0.80 cm 3 . The state of systemic disease at time of SRS, age and number of lesions were major prognostic factors in OS. Further investigation is warranted in order to define the optimal patient selection criteria and treatment parameters. PO-1256 Feasibility and initial results of Linac-based Stereotactic Body Radiotherapy in spinal metastases N. Giaj Levra 1 , M. Niyazi 2,3 , V. Figlia 1 , G. Napoli 1 , R. Mazzola 1 , L. Nicosia 1 , S. Corradini 2 , R. Ruggieri 1 , G. Minniti 4 , F. Alongi 1,5 1 IRCCS Ospedale Sacro Cuore-Don Calabria, Radiation Oncology, Negrar, Italy ; 2 University Hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany ; 3 German Cancer Consortium DKTK, German Cancer Consortium DKTK, Munich, Germany ; 4 San Pietro Hospital FBF, Radiation Oncology Unit- UPMC Hillman Cancer Center, Roma, Italy ; 5 University of Brescia, University of Brescia, Brescia, Italy Purpose or Objective Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) are well established local treatment approaches in several cancer settings. Although SBRT is still under investigation for spinal metastases, promising results in terms of a high effectiveness and optimal tolerability have been recently published on this topic. For spinal SBRT, one of the most relevant issues is represented by the inter-observer variability in target definition. Recently, several technological innovations, including specific tools such as multimodality-imaging (computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET-CT), automated volumes contouring and planning, could allow clinicians to minimize the uncertainties related to spinal SRS/SBRTSBRT workflow. Aim of this study is to report the feasibility of the clinical application of a dedicated software (Element®, BrainlabTM Germany) for spinal metastases SRS/SBRTSBRT Material and Methods The patient selection criteria for SRS/SBRTSBRT in spinal metastases were the following: age > 18 years, diagnosis of spinal metastases (n ≤ 3), life expectancy >3 months, controlled primary tumor or synchronous diagnosis and Spinal Instability Neoplastic Score (SINS) ≤ 12 points. All radiation target volumes were defined and planned with the support of the dedicated software Elements® (BrainlabTM Germany). Different dose prescription have been used: 12 Gy in single fraction, 12 Gy, 18 Gy, 21 Gy and 24 Gy in 3 fractions. Dose prescription ranged between 12 Gy in single fraction and 24 Gy in 3 fractions. Toxicity was assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) v4.0. SPSS version 20 was used for statistical analysis Results From April 2018 to April 2019, 54 spinal metastases in 32 recruited patients were treated with Linac-based SRS/SBRTSBRT. With a median follow-up of 6 months (range 3-12), local control rates at 3 months, 6 months and 9 months were 94%, 86% and 86%, respectively. No adverse events ≥ 3 grade higher than grade 2 were observed Conclusion This preliminary experience shows that with respect to acute toxicity and early clinical response, Linac-based SRS/SBRT using Elements® Spine SRS is a feasible and effective approach. Moreover, this technique demonstrated to be a easily adoptable tool to minimize potential inter-observer variability, time to treatment preparation and offers an accurate target definition and treatment planning.