ESTRO 2024 - Abstract Book

S1926

Clinical - Mixed sites, palliation

ESTRO 2024

37%), bone (16 patients; 23%), visceral organs/soft tissue (16 patients, 23%) and lymph nodes (13 patients, 18%). SBRT dose of 35 Gy in 5 fractions (IQR 30-39 Gy) was most frequently used.

Median follow up was 1.03 years (IQR 0.68-1.85). Local control of treated OP disease at 1-year was 84% (95% CI 90.7 72.4%) for the entire population, and was 85%, 96%, and 67% for GU, breast, and GI, respectively (p=0.12). Distant failure incidence was 66.7% (95% CI 56.2-79.2%) for the entire cohort at 1-year and was 61%, 63%, and 86% for GU, breast, and GI, respectively (p=0.09). At 1-year, for the entire population the cumulative incidence of systemic therapy change was 46.2% (95% CI 35.6-59.8%), and for GU, breast and GI were 44%, 41%, and 60%, respectively (p=0.23). The median time to change in systemic therapy was 0.5 years (IQR 0.25-0.73) for GU, 0.5 years (IQR 0.38 0.97) for breast, and 0.38 years (IQR 0.15-0.5) for GI. Twenty-seven (38%) patients died, including 20 (74%) of their cancer, with Kaplan-Meier estimated overall survival rate of 75.7% at 1-year (95% CI 65.9-86.9%), which significantly differed between cancer type (GU 87%, breast 96%, GI 22%, log rank p <0.001). On multivariable analysis, only cancer type was associated with overall survival, with GI cancers having worse survival compared to breast cancers (HR 0.11, 95% CI 0.03-0.4, p <0.001) and GU cancers (HR 0.12, 95% CI 0.04-0.36, p <0.001).

SBRT was well tolerated and there were no grade 4-5 acute or late toxicities by last follow-up.

Conclusion:

SBRT for OP disease delayed change in systemic therapy in approximately half of patients at 12 months and a third had no distant failure. This was marginally better for those with GU and breast cancers. Overall survival differed significantly between primary tumour diagnosis, with worse outcomes seen in patients with GI cancers. Future research to optimize patient selection, and response predictors is needed to determine which patients may derive benefit from this treatment strategy.

Keywords: oligoprogression, metastatic, SBRT

1517

Digital Poster

Intramedullary and leptomeningeal-epidural metastases. Outcomes of a rare and ominous condition.

Yuanyuan Lin, Héctor Pérez Montero, Laura Martínez Ávila, Andrea Álvarez Renuncio, Miguel Alonso Becerra, Margherita Moretti, Marc Ruiz Domínguez, Alicia Lozano Borbalas, Ferran Ferrer González, Cristina Gutiérrez Miguélez, Ferran Guedea Edo, Miquel Macià Garau, Anna Lucas Calduch, Arturo Navarro Martín

Hospital Duran i Reynals, Institut Català d’Oncologia (ICO) - L’Hospitalet de Llobregat, Radiation Oncology Department, Barcelona, Spain

Purpose/Objective: