ESTRO 2025 - Abstract Book

S1503

Clinical – Mixed sites & palliation

ESTRO 2025

adequate support for those undergoing curative treatment is essential for effective therapy completion and improved prognosis.

Keywords: discontinuation, complications, quality

1989

Proffered Paper Phase II randomized trial of elective versus involved target irradiation in stereotactic spine radiosurgery (NCT04033536) Yi-Lun Chen 1,2 , Shih-Fan Lai 3,2 , Wen-Chi Yang 3,2 , Shao-Lun Lu 3,2 , Hsing-Min Chan 2 , Wei-Hsin Lin 4 , Fon-Yih Tsuang 5 , Furen Xiao 5 , Feng-Ming Hsu 3,2 1 Oncology, National Taiwan University Biomedical Park Hospital, Hsinchu, Taiwan. 2 Oncology, National Taiwan University Hospital, Taipei, Taiwan. 3 Radiation Oncology, National Taiwan University Cancer Center, Taipei, Taiwan. 4 Orthopedic Surgery, National Taiwan University Hospital, Taipei, Taiwan. 5 Surgery, National Taiwan University Hospital, Taipei, Taiwan Purpose/Objective: Stereotactic spine radiosurgery (SSRS) has been rapidly adopted in clinics. To utilize SSRS, appropriate delineation of the target is important to radio-oncologists. The International Spine Radiosurgery Consortium (ISRC) has proposed delineation guideline to treat the tumor and adjacent spinal structures. Due to a lack of solid trials to support the proposal, we designed this randomized study comparing two SSRS treatment volumes to determine which results in the least protocol-specified treatment failure at 6 months after SSRS. Material/Methods: Patients with unirradiated spine metastases not requiring surgery were enrolled and randomized 1:1 to receive elective (EF) or involved (IF) target radiosurgery with 16 Gy in 1 fraction. The elective target was defined as the spinal tumor with nearby anatomic classification according to the ISRC guideline. The involved target was limited to the spinal tumor with an isotropic 8-mm margin, but extraosseous expansion was not allowed. This study was designed to detect a protocol-specified treatment failure rate > 10% at a significance level of 0.05 (two-sided) and 90% power. Treatment failure was defined as the presence of ≥ grade 3 toxicities or local progression indicative of surgery or re irradiation. Results: Between August 2019 and May 2024, 106 patients were enrolled for SSRS to 164 spinal metastases. Majority of the tumors were located at thoracic spine (89 sites), followed by lumbar (42 sites), cervical (20 sites) and sacrum (13 sites). Most patients (89%) had lung cancer. Fifty-two patients and 54 patients were randomized to EF and IF, respectively. Median follow-up time was 39.2 months (IQR, 20.6 – 50.1 months). At 6 months, 2 patients in EF and 3 patients in IF arm experienced treatment failure. Cumulative incidence of treatment failure at 6- and 12-month between EF and IF arm were 3.8% versus 5.7% and 3.8% versus 12% ( p =0.026), respectively. Median treatment failure-free survival was 46 months in EF arm and 21.6 months in IF arm. Overall survival at 6- and 12-month between EF and IF arm were 94.2% versus 88.7% and 86% versus 70.1% ( p =0.11), respectively. Only two patients (one in each arm) experienced ≥ grade 3 vertebral compression fracture and underwent vertebroplasty at 1.9 months and 21.6 months after SSRS, respectively.