ESTRO 2021 Abstract Book

S867

ESTRO 2021

Conclusion SIMT radiotherapy delivered in 3 fractions offers good local control and acceptable toxicity profile in the treatment of multiple brain metastases allowing for no systemic treatment interruptions.

PO-1040 Brain metastasis recurrence for SRS in non-previously radiated patients A. La Rosa de los Ríos 1 , L. Arribas 1 , M. Chust 1 , V. Crispin 2 , J.L. Guinot 1 , B. Quiles 1 , S. Canos 1 , Y. Murria 1 , E. Arana 3 , M.J. Perez 1 1 Instituto Valenciano de Oncologia, Radiation Oncology, Valencia, Spain; 2 Instituto Valenciano de Oncologia, Radiation Physics, Valencia, Spain; 3 Instituto Valenciano de Oncologia, Diagnostic Radiology, Valencia, Spain Purpose or Objective Our main objective was to evaluate brain metastasis recurrence in patients treated with Stereotactic Radiosurgery (SRS), despite the number of lesions, in non-previously radiated patients. Materials and Methods From January to December 2019, we collected all SRS exclusive treatment performed, from which, we selected patients with no previous brain radiation. A LINAC frameless with conformal arcs technique was used to administer the treatment. Progression-free survival was evaluated as a primary endpoint by a Kaplan-Meier and Log-rank test. Results Fifty-six lesions in twenty-two patients with a median age of 62 years (43-84) exclusively treated with SRS, with single or multiple (until 7) brain metastasis, in whom no brain radiation was administrated previously were found. With a median follow-up of 10 (1-23) months we found an overall survival of 68,2%. A 9 months (3,7-14.3) median BPFS was estimated. The median administered dose per lesion was 20Gy (18-20). When we consider different risk factors, we found a statistical significance of PFS with the number of lesions (>2 lesions; p=0,026). Other risk factors such as primary tumor origin, age, volume of lesions, time from brain metastasis to SRS, time from primary tumor diagnosis to development of bran metastasis, extracranial metastasis at the time of SRS or clinical symptomatic lesions, didn’t reached statistical significance. A total of 13 patients were found to develop recurrent brain lesions, from which 4 (30,8%) progressed in the same treated target. Furthermore radio-necrosis was found in 5 patients, 3 of whom developed a recurrence and received even more radiation (2 WBI, 1 stereotactic fractionated radiation), possibly contributing with the complication.