ESTRO 2021 Abstract Book

S860

ESTRO 2021

Conclusion Larger volume of metastases (> 2cc) was associated with significantly worse LC and OS rates following SRS to brain metastases from a range primary tumour sites. In keeping with the ability to deliver a higher BED to smaller volume metastases, BED10 >60Gy was also associated with improved OS. PO-1032 Effects of SRS in patients affected with brain metastases from NSCLC: a single institution report I. Chiovatero 1 , C. Mantovani 1 , A. Vella 1 , G.C. Iorio 1 , E. Orlandi 1 , M. Cerrato 1 , C. Cavallin 1 , S. Badellino 1 , A. Gastino 1 , E.M. Cuffini 1 , M. Levis 1 , U. Ricardi 1 1 University of Turin, Department of Oncology, Torino, Italy Purpose or Objective To evaluate the role of radiosurgery (SRS), alone or combined with whole-brain irradiation (WBI), in patients with oligometastatic non-small cell lung cancer (NSCLC), pointing out prognostic factors that might help clinicians in the choice of a “tailored” therapy. Materials and Methods We retrospectively analysed the data of all consecutive patients treated with SRS for brain metastasis (BM) at our Institution between 2012 and 2018. Local control (LC) of treated lesions, loco-regional brain control (LRC), progression free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Chi- squared test was used to examine between-group covariate differences, and the Cox proportional hazards model was used for univariate and multivariate analysis to assess the effects of clinical/treatment variables on clinical outcomes. Results Overall, we treated 299 lesions in 201 patients. The median age was 65 years (range 39-88) and 125 were male (62%). Predominant histology of the primary tumor was adenocarcinoma (156 patients, 78%). 102 patients (51%) had supratentorial BM, 27 (13%) patients had infratentorial BM, while 72 (36%) remaining patients had both supratentorial and infratentorial BM. The median volume of BM was 2.53cc (range 0.16-84.67cc). 90 patients (45%) were on corticosteroid treatment (CST) for neurological symptoms before SRS. Prescription dose was ≥21Gy in 166 patients (83%). Concomitant or sequential WBI was given to 23 patients (11%). Adjuvant SRS to the surgical cavity of a resected BM was performed in 21 patients (Table 1). With a median follow up of 13 months, we observed 1-yr LC, LRC, PFS and OS of 78%, 48%, 26% and 60%, respectively (Figure 1). After multivariate analysis we observed a lower LC for non-adenocarcinoma histology (HR: 2.095, p=0.033) and a better LC for lesions treated with ≥21Gy (HR: 0.395, p=0.011). The need of CST before SRS (HR: 1.538, p=0.041) and the presence of at least 1 infratentorial BM (HR: 1.786, p=0.008) negatively affected LRC, while the addition of WBI had a positive impact (HR: 0.263, p=0.005). The negative prognostic role of infratentorial location and of the need for CST were also observed for PFS and OS. An overall intracranial tumor burden >3.5cc at the time of SRS (HR: 1.550, p=0.021) and a progression of systemic disease (HR: 2.132, p<0.001) also had a negative impact on OS.