ESTRO 2020 Abstract Book

S662 ESTRO 2020

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. PO-1257 Use of Stereotactic Radiotherapy in lymph nodes for oligometastic pelvic tumors A. Rese 1 , F. Pastore 1 , M. Conte 1 , G. Ciaglia 1 , F. Francomacaro 1 , V. Iorio 1 1 Emicenter, Radiotherapy, Casavatore, Italy Purpose or Objective Oligometastatic desease has been defined as a state with 5 or fewer clinically detectable metastases. Patients with oligometastatic or oligorecurrence in lymph nodes could be cured with local therapy such as stereotactic body radiotherapy (SBRT). SBRT represents an emerging strategy. The aim of this retrospective study was to evaluate the oncological outcome and pattern of recurrence in patients treated with stereotactic body radiation therapy (SBRT) to lymph node metastases. Material and Methods In this mono-institutional analysis, patients with a maximum of three lymph node metastases from prostate cancer, bladder cancer and endometrial cancer treated with SBRT were included. All patients had a positive 18F-Choline PET/CT in case of prostate cancer or a positive 18FDG PET/CT in the other cases.

Primary endpoints of the analysis were acute and late toxicities. Secondary endpoints were local control (LC), progression-free survival (PFS) and overall survival (OS). Results 26 patients were eligible and treated with SBRT from January 2016 to January 2019 and retrospectively analysed. 13 patients had prostate cancer, 7 bladder cancer and 6 endometrial cancer. 9 patients (69%) with prostate cancer had undergone radical prostatectomy. A total of 30 lesions were treated: 23 patients had one metastasis, while 2 patients had two metastasis and 1 had three metastasis. Patients' median age was 70.8 years (range 51-84). Median follow up was 16 months. The dose delivered to the target ranged from 24 to 35 Gy in 3-5 fractions; 8 Gy daily in 3 fractions, 10 Gy daily in 3 fractions or 7 Gy in five fractions. Toxicity was rare: 23 patients (88%) presented G1 genitourinary acute toxicity, 20 patients (77%) presented G1 gastrointestinal acute toxicity, none had G3 acute toxicity. No patients developed grade ≥2 late toxicity. Local control was achieved in 95%. LC at 1 was 91%. Two- years progression-free survival was 60% and the overall survival was 75%. Conclusion SBRT is an effective and well-tolerated treatment option in the management of lymph node metastases. A greater number of cases could help us better stratify patients, that could benefit from a dose or fractionation. PO-1258 Intensity modulated radiation therapy for lymph node oligo-recurrence A. Sato 1,2 , M. Omura 2 , Y. Minagawa 2 , K. Takino 2 , K. Matsui 2 , H. Hongo 2 , R. Shirata 2 , H. Hashimoto 3 , T. Misumi 4 , Y. Sasaki 5 , T. Inoue 6 , M. Hata 7 1 Yokohama City University Hospital, Radiation Oncology, Yokohama, Japan ; 2 Shonan Kamakura General Hospital, Radiation Oncology, Kamakura, Japan ; 3 Shonan Fujisawa Tokushukai Hospital, Radiation Oncology, Fujisawa, Japan ; 4 Yokohama City University Medical Center, Biostatistics, Yokohama, Japan ; 5 Shonan Kamakura General Hospital, Center for Clinical and Translational Science, Kamakura, Japan ; 6 Shonan Kamakura General Hospital, Advanced Medical Center, Kamakura, Japan ; 7 Yokohama City University Graduate School of Medicine, Radiation Oncology, Yokohama, Japan Purpose or Objective Oligo-recurrence is a special case of oligometastases in which patients have limited number of metastatic lesions with a controlled primary tumor and local therapy may improve their prognosis. In this report, we evaluated the role of intensity modulated radiation therapy (IMRT) on the clinical outcomes of patients with lymph node oligo- recurrence. Material and Methods We retrospectively reviewed the medical records of 21 patients who had been diagnosed with lymph node oligo- recurrence and received IMRT between October 2010 and August 2017. Inclusion criteria were as follows: 1) oligo- recurrence occurred exclusively in the lymph nodes, 2) patients were treated with curative intent and 3) primary lesions were controlled. Results The median age at the start of IMRT for lymph node oligo- recurrence was 67 years (range: 39 to 81 years). Sites of primary lesions were the following: lungs 5, breasts 4, uterine 4, esophagus 2 and others 6. Primary histopathology was adenocarcinoma in 8 patients, squamous cell carcinoma in 5 patients and others in 8 patients. The location of the recurrent lymph node was regional only in 14 patients (66.7%), distant only in 6 (28.6%), and both regional and distant in 1 patient (4.8%). The gross tumor volume (GTV) included all detectable involved lymph nodes. The number of lymph nodes