ESTRO 2024 - Abstract Book

S1974

Clinical - Mixed sites, palliation

ESTRO 2024

2537

Mini-Oral

Validation of distant metastasis velocity as a prognostic score in oligometastatic cancer patients

Jonas Willmann 1 , Sarah Baker 2 , Hanbo Chen 3 , Eugenia Vlaskou Badra 1 , Sebastian M. Christ 1 , Michael Mayinger 1 , Maiwand Ahmadsei 1 , Selma Adilovic 1 , Subhadip Das 2 , Linden Lechner 2 , Wei Liu 2 , Mitchell Liu 2 , Benjamin Mou 2 , Tanya Berrang 2 , Devin Schellenberg 2 , Scott Tyldesley 2 , Darby Erler 3 , Kristin Redmond 4 , Umberto Ricardi 5 , Matthias Guckenberger 1 , Arjun Sahgal 3 , Robert Olson 2 , Nicolaus Andratschke 1 1 University Hospital Zurich, Department of Radiation Oncology, Zurich, Switzerland. 2 University of British Columbia, Department of Radiation Oncology, British Columbia, Canada. 3 Sunnybrook Odette Cancer Centre, Department of Radiation Oncology, Toronto, Canada. 4 Johns Hopkins University, Department of Radiation Oncology and Molecular Radiation Sciences, Baltimore, USA. 5 University of Turin, Department of Oncology, Turin, Italy Cancer patients with oligometastatic disease may undergo metastasis-directed local ablative therapies with the aim of achieving durable disease control and prolonged survival in selected cases. However, there is a substantial risk for these patients to develop new metastases following local therapy. There is a paucity of validated prognostic scores for post-progression scenarios, yet such scores could inform treatment decision-making. Distant Metastasis Velocity (DMV), defined as the number of new metastases per month at the time of distant failure (mets/mo) after metastasis-directed stereotactic body radiotherapy (SBRT), has been proposed a novel post progression prognostic score in patients with oligometastatic disease, based on a single-center retrospective study (retrospective discovery cohort [RDC]) [1]. The objective of this study was to externally validate the prognostic significance of DMV. The prognostic value of DMV for overall survival (OS) and widespread-failure-free survival (WFFS, defined as more than 5 lesions at distant failure) among cancer patients with oligometastatic or oligoprogressive disease (maximum 5 lesions) who received initial SBRT to all lesions and developed distant failure thereafter was validated in two independent cohorts: the prospective multicenter non-randomized phase 2 SABR-5 trial (NCT: NCT02933242) (prospective validation cohort, PVC), and the retrospective multicenter CORE study (retrospective validation cohort, RVC). Within the RVC, the lesion count at distant failure was not available for patients with disseminated progression; thus, only those with a limited number of new lesions were included. WFFS was only determined for the subgroup of patients presenting with repeat oligometastatic disease at first distant failure, defined as a maximum of 5 lesions. Patients were stratified into low (<0.5mets/mo), intermediate (0.5-1.5mets/mo), and high (>1.5mets/mo) DMV groups. OS and WFFS were determined from the time of first distant failure after initial SBRT to all metastatic lesions until death or progression with more than 5 lesions, respectively. Time-to-event curves for OS and WFFS were generated utilizing the Kaplan-Meier method, with log-rank tests employed to assess statistically significant differences. The discriminatory strength of DMV for OS was analyzed using Gönen & Heller’s concordance Purpose/Objective: Material/Methods: