ESTRO 2024 - Abstract Book

S1665

Clinical - Lung

ESTRO 2024

Ilaria Morelli 1 , Oulimata Dieng 2 , Mauro Loi 1 , Gabriele Simontacchi 1 , Carlotta Becherini 1 , Daniela Greto 1 , Emanuela Olmetto 1 , Pietro Garlatti 1 , Icro Meattini 1 , Erika Scoccimarro 1 , Giulio Francolini 1 , Isacco Desideri 1 , Marianna Valzano 1 , Luca Visani 1 , Vanessa Di Cataldo 1 , Viola Salvestrini 1 , Valentina Luzzi 3 , Sara Tomassetti 3 , Raffaella Doro 4 , Laura Masi 4 , Lorenzo Livi 1 1 Azienda Ospedaliero-Universitaria Careggi, Radiation Oncology, Florence, Italy. 2 Tenon Hospital, Radiation Oncology, Paris, France. 3 Azienda Ospedaliero-Universitaria Careggi, Interventional Pneumology, Florence, Italy. 4 Istituto Fiorentino di Assistenza e Cura (IFCA), Medical Physics, Florence, Italy

Purpose/Objective:

The role of SBRT in the setting of oligometastatic disease (≤ 5 lesions) is well established, but its applicability in mediastinal nodal lesions is debated, due to proximity of mediastinal OARs and uncertainty in dose deliver due to respiratory motion. Real-time tumor tracking (RTTT) under guidance of fiducial markers (FM) implanted via EBUS may improve treatment delivery. We present preliminary data from patients treated with SBRT following EBUS guided FM placement.

Material/Methods:

We retrospectively collected data of oligometastic patients with miscellaneous metastatic primary tumours treated with Cyberknife robotic radiosurgery system for mediastinal nodal metastases from December 2021 to February 2023. Golden 25G FM were placed intralesionally via EBUS under general anesthesia and via rigid bronchoscopy. After 1 week patients underwent blank and contrast-enhanced CT for the treatment planning; in selected cases, a 4D-CT was acquired to evaluate the concordance between FM and the tumor motion along respiratory cycle. PTV was obtained from the GTV by a 3- 5mm geometrical expansion. Planning aim was to prescribe an ablative dose of ≥ 35 Gy in 5 fractions (EQD2 ≥ 50 Gy, α/β=10) using RTTT with the Synchrony system. In the subset of patients for whom 4D-CT was available, we evaluated intrafractional tumor shifts due to tumor motion and resulting changes in PTV size (ΔPTV) using an ITV -based strategy. Preliminary outcomes and acute and late toxicities were assessed.

Results:

Data from 12 patients and 13 tumors were reported. Median age was 73 years (48-89) and median follow-up 6 months (2-18). Primary tumor was lung (n=6), GI (n=3), breast (n=2) and prostate cancer (n=1). Tumor location was level 4 (n=4), 7 (n=3), 10 (n=3), 8 (n=1), 3 (n=1), 11 (n=1). Concurrent systemic therapy was prescribed in 7 patients. Median number of implanted FM was 3 (2-3). No peri-procedural toxicities were reported. No migration or malfunction were observed. No peri-procedural toxicities were reported. Median dose prescription was 35 Gy (25 40): the target dose of 35Gy in 5 fractions was not achieved in 2 patients due to prior lung irradiation and bronchial infiltration at bronchoscopy, respectively. Six-month Local Control (LC), Progression-Free Survival (PFS) and Overall Survival (OS) were 100%, 71% and 85%, respectively (fig1). No G3 acute toxicities were observed. Severe late adverse event occurred in one patient with initial aortic infiltration who developed fatal arterio-oesophageal fistula 5 months after SBRT. At subset analysis 6 patients with available pre-treatment 4D-CT were evaluated for intrafraction tumor motion. Results are summarized in Table 1. Median cranio-caudal (CC), latero-lateral (LL) and antero-posterior (AP) were 5.95 mm (3.3-6.4), 4.70 mm (2.9-5.6) and 2.9 mm (1.2- 6.5). ΔPTV was 25.89 cc (12.42 -39.19).