ESTRO 2024 - Abstract Book

S1793

Clinical - Lung

ESTRO 2024

outcomes. The primary endpoints were Local Control (LC), Nodal Relapse Free Survival (NRFS), Distant Relapse Free Survival (DRFS), Progression Free Survival (PFS) and Overall Survival (OS). Secondary endpoints were main acute and late toxicities. Pulmonary toxicity was defined with the CTCAE 5.0 grading. Post-SABR radiological outcomes were evaluated with the Ronden1 classification. Survival analyses were performed with Kaplan-Meier estimator in order to estimate LC, NC, SC, PFS and OS. Cox regression model was used to assess associations between covariates and clinical outcomes.

Results:

We retrospectively analysed a cohort of 212 very elderly patients. The median age was of 82 years (IQR: 81-84) and 76.9% were male. 62.7% of patients had no histological confirmation of the pulmonary lesion. The predominant histological type was adenocarcinoma (45 patients, 21.2%). Patients were treated according to a “risk adapted” fractionation schedule: 67 (31.6%) received 3 fractions (45-54 Gy), 84 (36.9%) received 5 fractions (50-55 Gy), 48 (22.6%) received 8 fractions (56-60 Gy). With a median follow-up of 27.5 months, 1, 2 and 3-year LC rates were 95.6 %, 94.1% and 93%, respectively ( Figure 1 A ). The rate of NRFS were 93% at 1 year and 90.3% at 2 and 3 years, while systemic control rates were inferior (1, 2, 3-year DRFS: 86.5%, 76.7% and 71.1%). The sites most frequently affected by the first metastasis were: ipsilateral lung (13,7%), contra-lateral lung or both lungs (21,6%) and brain (19.6%). In 92% of patients with systemic progression, the primary lesion treated with SABR was under control. PFS rates at 1, 2 and 3 years were 82.4 %, 72.2% and 66.6%, respectively. The median OS was of 42 months (1, 2, 3- year OS: 88.4%, 72% and 57.4%). Death was documented in 142 (67%) patients, mostly (76 patients, 59%) for non-neoplastic causes. In a Cox multivariable analysis, ECOG PS 1 (HR: 4.26; p = 0.007) and PTV >35 cc (HR 13.78; p = 0.012) showed a statistically significant association with a worse LC ( Figure 1 ). Pretreatment FEV1 ≥ 90% (HR 0.43; p < 0.001) and PTV ≤ 35cc (HR 1.63; p= 0.041) were associated with better OS. Only 2 cases of acute severe pneumonitis of grade 3 or higher were detected. 108 patients (54.5%) displayed early imaging abnormalities, mostly asymptomatic or with mild symptoms: 25 diffuse consolidations, 29 patchy consolidation, 17 diffuse Ground Glass Opacities (GGOs), 37 patchy GGOs. The modified fibrosis was the most frequent pattern of chronic radiological outcome (56.8%) ( Figure 2 ).

Figure 1 A) Local control (LC) of the entire cohort; B) LC stratified for ECOG PS; C) LC stratified for PTV; D) LC stratified for stage.