ESTRO 2021 Abstract Book

S506

ESTRO 2021

Conclusion We show for the first time that adding biological information ( RSI ) improves performance of patient stratification models for high-risk PCa. Our model suggests older patients with lower T-stage, baseline PSA and RSI who receive excess dose to SV tips have lower BCR. Admittedly RSI was not significant and had unlikely Hazard Ratios and confidence intervals which will become clearer in larger cohorts. These findings and differences between fractionation schedules suggest links between fractionation and biology that should be explored in larger cohorts. OC-0640 Dose-density interaction predicts local relapse and distant metastasis following lung SABR A. Davey 1 , M. van Herk 1 , C. Faivre-Finn 1 , J. Lilley 2 , F. Sun 3 , K. Franks 3 , A. McWilliam 1 1 The University of Manchester, Division of Cancer Sciences - Faculty of Biology, Medicine and Health, Manchester, United Kingdom; 2 Leeds Cancer Centre, Department of Medical Physics, Leeds, United Kingdom; 3 Leeds Cancer Centre, Clinical Oncology, Leeds, United Kingdom Purpose or Objective Predictors for local relapse (LR), regional progression (RP) and distant metastasis (DM) after lung SABR are needed. CT density biomarkers predict microscopic disease risk, and LR/RP if minimum dose <1.5cm from the GTV is low (Salguero,2013). Low dose at 3cm predicts DM (Diamant,2018). The continuous interaction of dose and density has not been studied.