ESTRO 2023 - Abstract Book

S1894

Digital Posters

ESTRO 2023

Conclusion We have shown that established normalisation methods can suppress or enhance subtle changes in radiomic FTs across treatment: this suggests that methods developed on single timepoints may not be suitable for longitudinal data. Despite large changes in trajectories, normalisation has little impact on the number of FTs remaining after application of a FT selection pipeline tailored to longitudinal data. We preliminary recommend using the Psoas muscle for normalisation as it produced the most consistent FT selection across patients. Further work is needed to investigate the impact this has on predictive capabilities of radiomic models.

PO-2110 Normalised odds ratios help understand the relative importance of dose in multivariable models

E. Dalqvist 1 , T. Rancati 2 , H. Ólafsdóttir 3 , G. Gagliardi 1 , G. Alexandersson von Döbeln 3 , M. Nilsson 3 , F. Klevebro 3 , E. Onjukka 4

1 Karolinska University Hospital , Department of Medical Radiation Physics and Nuclear Medicine, Stockholm, Sweden; 2 Fondazione IRCCS Istituto Nazionale dei Tumori, Prostate Program, Milano, Italy; 3 Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Stockholm, Sweden; 4 Karolinska University Hospital, Department of Medical Radiation Physics and Nuclear Medicine, Stockholm, Sweden Purpose or Objective The odds ratio (or hazard ratio) of dose/volume parameters is often low in comparison to non-dosimetric variables in multivariable prediction models. As the odds ratio takes the inverse of the unit of continuous variables (e.g. % increase per Gy), the default units of the DVH could systematically fail to highlight the relative importance of the DVH as a predictor of normal-tissue complications. Normalisation of odds ratios for continuous variables offers a less arbitrary way of presenting