ESTRO 2021 Abstract Book

S890

ESTRO 2021

volumes compared to Gd-T1 or DCE-MRI are associated with favourable outcome.

PO-1068 SRS in brain metastases from breast cancer: a single-centre retrospective study R. Ching-López 1 , M. Zurita 1 , P. Vargas 1 , R. del Moral 1 , J. Expósito Hernández 1

1 Hospital Virgen de las Nieves, Radiation Oncology, Granada, Spain

Purpose or Objective To analyse results in local control and survival after stereotactic radiosurgery (SRS) and identifying prognostic factors in patients treated in our centre for brain metastases from breast cancer. Materials and Methods We retrospectively reviewed a total of 101 patients with breast cancer brain metastases treated with SRS between June 1996 and April 2019. Post-radiosurgery survival and related prognostic factors were analyzed using Cox regression analysis. Results The median age of the patients was 51 years (26-75). Most of the patients (94.8%) received a dose ≥18 Gy. The median post-radiosurgery survival was 14 months, with local control of the treated lesion in 86.9% of the patients. The prognostic factors related to survival in the bivariate analysis were RPA, GPA and KPS, as well as number of metastases at diagnosis. However, only the last two factors showed a statistical association in the multivariate analysis. Conclusion Radiosurgery is an effective and safe treatment with high local control in patients with selected breast cancer brain metastases. The most important prognostic factor for survival was KPS. PO-1069 Multiple Brain Metastases concomitantly treated with robotic SRS/SRT A. Sanchez Galvan 1 , A.M. Deli 2 , A. Fodor 2 , R. Tummineri 2 , S.L. Villa 3 , S. Baroni 4 , G. Mandurino 5 , P. Pacifico 3 , C.L. Deantoni 2 , N. Slim 2 , F. Zerbetto 2 , C. Fiorino 6 , S. Broggi 6 , A. Del Vecchio 6 , S. Arcangeli 7 , N.G. Di Muzio 8 1 IRCCS San Raffaele Scientific Institute , University of Milano-Bicocca, Radiation Oncology, Milano, Italy; 2 IRCCS San Raffaele Scientific Institute, Radiation Oncology, Milan, Italy; 3 IRCCS San Raffaele Scientific Institute, University of Milano-Bicocca, Radiation Oncology, Milan, Italy; 4 IRCCS San Raffaele Scientific Institute , University of Milano-Bicocca, Radiation Oncology, Milan, Italy; 5 IRCCS San Raffaele Scientific Institute, University of Milano-Bicocca, Radiation Oncology, Milan, Italy; 6 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 7 University of Milano-Bicocca, Radiation Oncology, Milan, Italy; 8 IRCCS San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Radiation Oncology, Milan, Italy Purpose or Objective Objective: To increase the quality of life of patients with multiple brain metastases, stereotactic radiosurgery (SRS)/ stereotactic radiotherapy (SRT) is increasingly used. Here we report our experience with robotic SRS/SRT concomitanly delivered to multiple (≥5) brain metastasis. Materials and Methods Methods: From March 2018 to December 2020 a total of 269 brain metastases in 24 pts (13 females and 11 males) were treated with a single treatment plan SRS/SRT in our institution. Primary site of tumors was lung in ten pts, breast in six pts, melanoma in four pts, kidney in one patient, two patients had lung and breast cancer and another one had lung and prostate cancer. Five pts previously underwent Whole Brain Radiotherapy (WBRT). Gross target volume (GTV) and organs at risk (OAR) were defined on fused computer tomography (CT) and contrast-enhanced T1-weighted MRI images. Planning target volume (PTV) was defined adding a 1 mm margin to GTV. All fractions were delivered in consecutive days. All pts received preventive steroid therapy; median dose was 4 mg/day (2-16 mg). Toxicity was scored in accordance with the CTCAE scale v.4.0. Patients were followed-up with contrast-enhanced MRI every 3 months. Results Results: Patient's median age was 51.6 (29-84) years and median Karnofsky Performance Score (KPS) was 90% (70-100). Median number of brain metastasis was 8 (6-46). The median of the sum of the GTV volumes per patient was 6 cm3 (0.49-22.33 cm3), and the median of the sum of the PTV volumes 9.84 cm3 (1.54-33.18 cm3). Median prescribed dose was 32.5 (21-37.5) Gy, at a median isodose of 78% (65%- 89%), in a median number of 5 (1-5) fractions. Median estimated treatment delivery time was 74 (38-143) minutes, but the actual treatment time was reduced by about a third. Acute toxicity was observed in 3 patients and was limited to grade 1 neurological events represented by dizziness and paresthesia. With a median follow up of 5 months (0.49-15.7 months), one patient developed symptomatic radionecrosis controlled with corticosteroids. Fourteen pts presented local control and four patients had progression/pseudoprogression of the lesions. Four pts had intracranial progression due to new lesions. Six pts were unavailable for follow up: 3 pts were dead for systemic progression, 1 patient died with heart failure two weeks after the treatment and 2 pts were lost to follow-up. At the last follow up, 11 pts were dead, 5 with systemic progression, 5 with intracranial progression and 1 with heart failure. Conclusion Conclusions: In our experience, concomitant robotic SRS/SRT for patients with multiple brain metastases is feasible with low toxicity and the possibility to repeat it as salvage treatment, but intracranial progression remains the main prognostic factor. PO-1070 The potential implications of proton planning technique for LET-related changes on MRI A. Bertolet 1 , R. Abolfath 2 , D. Carlson 3 , R.A. Lustig 3 , C. Hill-Kayser 3 , A. Michelle 3 , A. Carabe 4 1 Massachusetts General Hospital and Harvard Medical School, Radiation Oncology, Boston, USA; 2 New Jersey Urology, Radiation Oncology, West Orange, NJ, USA; 3 University of Pennsylvania, Radiation Oncology, Philadelphia, PA, USA; 4 Hampton University Proton Therapy Institute, Physics, Hampton, VA, USA