S824
Clinical - Lung
ESTRO 2026
Patient characteristics are shown in Table 1.
pre-study assumption and comparable to published results in PCI-treated cohorts, however the OS of brain metastases patients was shorter. The progression in the brain was observed early -most patients progressed during the first 12 months and almost all in 18 months. A MRI (not CT) before starting radical chemoradiotherapy should be done in all patients. A half of patients with brain progression can be treated with SRS instead of WBRT. Better ways to identify patients with high risk of brain involvement are urgently needed to offer them PCI instead of treating the whole LD-SCLC population. Keywords: Prophylactic cranial irradiation, Brain metastases Digital Poster Highlight 3761 Impact of prescription method on local control and side effects of stereotactic radiotherapy for pulmonary oligometastases Davide Franceschini 1 , Enrico Pozzo 1 , Andrea Bresolin 1 , Francesco La Fauci 1 , Ruggero Spoto 1 , Luca Dominici 1 , Antonio M Marzo 1 , Beatrice Marini 1 , Marie Lohmer 1,2 , Ciro Franzese 1,2 , Stefano Tomatis 1 , Pietro Mancosu 1,2 , Marta Scorsetti 1,2 1 Radiotherapy and Radiosurgery, IRCCS-Humanitas Research Hospital, Rozzano/Milan, Italy. 2 Biomedical Sciences, Humanitas University, Pieve Emanuele/Milan, Italy Purpose/Objective: Prescription strategies in stereotactic body radiotherapy (SBRT) vary widely, ranging from “homogeneous” dose (HD) distributions and “non- homogeneous” dose (NHD) prescriptions with higher in-target peaks. Although these approaches deliver the same nominal prescription dose, differences in dose heterogeneity may influence both tumor control and adverse events. This study evaluated outcomes of HD and NHD prescriptions for lung oligometastases. Material/Methods: Patients treated between 2014 and 2024 with 48 Gy in 4 fractions were included. Patients were categorized as HD (i.e. prescription to target mean, Dmax<105– 107%) or NHD (i.e., Dmax<125-150%). In both groups, the minimum target coverage dose was identical. Local progression-free survival (LPFS) was the primary endpoint. Survival times were calculated from the last day of SBRT. Side effects were scored according to CTCAE version 5.1. Contingency analyses were performed using a two-sided Fisher’s exact test. LPFS was assessed using Kaplan–Meier method, and comparisons were performed with log-rank (Mantel– Cox) test. Results: A total of 312 patients (452 lesions) were included.
After a median follow-up of 30 months, 42 patients (55 lesions) experienced local recurrence. Most recurrences occurred in the HD group (49 patients, 23% / 52 lesions, 15.6%). LPFS at 1, 2, and 3 years was 94.1%, 89.0%, and 84.0% in the entire cohort; 91.9%, 85.2%, and 78.6% in the HD group; and 98.9%, 97.8%, and 97.8% in the NHD group (HR 0.33; 95% CI, 0.17– 0.74; p = 0.0012) (Fig. 1).
Colorectal primary cancer was also significantly associated with a higher risk of local progression (HR 2.1; 95% CI, 1.2–3.7; p = 0.007). Induced and repeat oligometastases had a higher risk of local relapse (15.4% and 16.7%) compared with de novo oligometastases (6.0%) (p = 0.003). Similarly, a PTV volume >14.4 cc was associated with a higher local relapse rate (15.9% vs. 8.4%, p = 0.02). The multivariate model including these four variables retained statistical significance (p < 0.001). Acute and late side effects were mild and not influenced by prescription
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