ESTRO 2023 - Abstract Book

S1044

Digital Posters

ESTRO 2023

Conclusion DLCO is a useful marker to identify the patients who are at higher risk of mortality and infectious pneumonia among patients with NSCLC treated with definitive radiotherapy.

PO-1303 Fractionated stereotactic radiation therapy for brain metastases: Outcomes and patterns of failure

N. Farre 1 , A.M. Soto-Cambres 2 , S. Rabi 1 , N. Jornet 3 , J. Balart 1 , A. Vila 1 , J.V. Rojas 1 , E. Otero 1 , M. Majem 4 , I. Sullivan 4 , A. Barba 4 , P. Carrasco 3 , G. Sancho-Pardo 1 1 Hospital de la Santa Creu i Sant Pau, Radiation Oncology, Barcelona, Spain; 2 Hospital del la Santa Creu i Sant Pau, Radiation Oncology, Barcelona, Spain; 3 Hospital de la Santa Creu i Sant Pau, Medical Physics, Barcelona, Spain; 4 Hospital de la Santa Creu i Sant Pau, Medical Oncology, Barcelona, Spain Purpose or Objective To review outcomes and patterns of failure in patients treated with fractionated stereotactic radiotherapy (FSRT) for brain metastases in the setting of oligometastatic (OM) or oligoprogressive (OP) disease. Risk factors for failure in local control, disease-specific survival and brain-progression free survival were identified in a single institution retrospective study. Materials and Methods 103 brain metastases from 74 patients treated with FSRT alone or adjuvant to surgery (25%) from 2018 to 2022 were included in the study. Dose, PTV volume, tumor location, metastatic status and immune checkpoint inhibitor (ICI) treatment were collected. Kaplan-Meier method was used for survival analysis and a multivariate analysis with Cox's regression was applied to investigate the risk factors. Results In the studied series, 90% of primary tumors were lung cancer and 10% other types. 62% lesions were OM ( ≤ 5 lesions), 22% OP ( ≤ 5 lesions) and 16% OM brain disease in a context of polimetastatic disease before systemic treatment. 59% received concomitant, pre or post FSRT ICI treatment. Prescription doses ranged from 25 to 35 Gy, delivered in 3-8 fractions (BED10 range: 37.5-59.5 Gy). Median planning target volume was 9.6cc (range:1.1-64cc). Median follow-up was 11 months (range 1-52). 1 and 2 years local control (LC) rates were 83% and 65% in FSRT alone and 95% and 88% in adjuvant FSRT, respectively. Table 1. Concomitant or pre-FSRT ICI was associated with improved local control (p= 0.013), suggesting a synergistic interaction between FSRT and ICI therapies. Disease-specific survival (DSS) at 1 and 2 years was 91.8% and 77% in FSRT alone and 81% and 67% in adjuvant FSRT. Oligoprogressive or polimetastatic status at diagnosis and infratentorial location were associated with worse DSS (p=0.025, p=0.009, p=0.035, respectively).