ESTRO 2023 - Abstract Book

S1295

Digital Posters

ESTRO 2023

Conclusion Lung is the most prevalent tumor between the patients that died in the first 30 days after treatment. Lung cancer was the tumor with the highest 15DMR. Lung, colorectal and gastroesophageal tumors had a 30DMR higher than the recomended 20%. This could indicate that it could be a factor in the decision whether to treat these patients. On the other side prostate cancer had a 0% 15 and 30 DMR so it seems correct to offer palliative radiotherapy to this group. Further investigation is needed in order to find other prognostic factors that help us decide which patients we should offer palliative radiotherapy.

PO-1595 Stereotactic Body Radiotherapy (SBRT) for Spinal Metastases

F. Ferrario 1,2 , M. Torrisi 1,2 , C. Chissotti 1,2 , L. Giannini 1,2 , C.L. Deantoni 1 , S. Broggi 3 , M. Midulla 1,2 , S.L. Villa 1,2 , I. Dell'Oca 1 , A. Fodor 1 , C. Fiorino 3 , A. Del Vecchio 3 , S. Arcangeli 4,2 , N.G. Di Muzio 1,5 1 IRCCS San Raffaele Scientific Institute, Department of Radiation Oncology, Milan, Italy; 2 Università degli Studi di Milano Bicocca, School of Radiation Oncology, Milan, Italy; 3 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 4 ASST Monza, Department of Radiotherapy, Monza, Italy; 5 Università Vita-Salute San Raffaele, Faculty of Medicine and Surgery, Milan, Italy Purpose or Objective Spine is a common site of metastatic bone disease and represents a challenging treatment for radiation oncologists due to the presence of the spinal cord as close organ-at-risk. The aim of this study is to report our experience with robotic SBRT for the treatment of spine metastases, evaluating different fractionation schedules, in terms of efficacy and toxicity. Materials and Methods This retrospective study includes a total of 133 treatments in 79 patients (pts), delivered between October 2017 and November 2021, on spine metastases. Patient’s median age was 72 (21-91) years at the time of SBRT. Primary tumor was prostate in 45 pts, breast in 10 pts, lung in 8 pts, and other primary tumors in the remaining pts. SBRT was delivered with CyberKnife® (Accuray, Sunnyvale, CA, USA) real-time tracking radiation therapy. Depending on the metastasis location, Clinical Target Volume (CTV) was defined as whole vertebral body +/- pedicles +/- posterior elements, according to the International Spine Radiosurgery Consortium consensus guidelines. Different fractionation schedules were used and compared: single fraction (fx) for 90 treatments versus 3-5 fx for 43 treatments. In the single fx the median prescription dose was 18 (16-20) Gy, to the median isodose of 79 (70-83) %. In the fractionated treatments, median prescription dose was 27 (24-35) Gy, to the median isodose of 79 (70-82)%. Forty-nine pts were treated with precautional steroid therapy at the time of RT. Toxicity assessment was based on CTCAE version 5.0 criteria. Results Median follow-up was 37.8 (1.1-60.2) months. No grade (G) ≥ 3 acute toxicity was observed. One patient suffered from G2 hyposthenia and paresthesia of the lower limb, three pts experienced G1 back pain, one patient had G1 nausea. No late toxicity was observed. Overall Survival (OS) at 12- and 24- months was 84.7%, and 62.7%, respectively. Kaplan Meier estimates of local relapse free survival (LRFS) was 86.1% at 12 months, 77.5% at 24 months, 71.9% at 48 months and 67.4% at 60 months (See Fig. 1). Median distant metastases free survival (DMFS) was 9.3 months. A trend for a significant difference (p=0.06) in distant metastases-free survival (DMFS: 10.3 vs 8.4 months, respectively) in favor of single versus multiple SBRT fractions was observed (See Fig. 2). In the single fx group 47.8% of pts had up to four metastases, while in the 3-5 fx group 51.2% of pts had up to four metastases. Before treatment 36 pts were symptomatic, and after SBRT 89% of them presented a complete pain response.