ESTRO 2023 - Abstract Book

S1907

Digital Posters

ESTRO 2023

Materials and Methods Two-hundred fifty-four patients treated for prostate cancer with intensity-modulated RT at 2 Gy/fraction and belonging to STIC-IGRT and PROFIT trials (ref) were analyzed as part of a collaborative research project between Research Group 1 (RG1) and Research Group 2 (RG2). Patients were scored for acute ( ≤ 3 months) and late (> 3 months) urinary toxicity (incontinence, retention, dysuria, hematuria) using the CTCAE v.3.0. Planning dose maps were spatially normalized to a common reference anatomy and VB analyses were first completed by RG1 (Mylona et al 2019). To perform an independent comparison, RG2 used a recently developed tool for VB statistical analysis. In detail, for each toxicity outcome, a generalized linear model (GLM) was designed to include dose maps: non-parametric permutation tests accounting for multiple comparisons were performed, and the significance p -map was generated. Results The RG2 VBA identified regions of significant association between dose and acute incontinence, late dysuria, late hematuria and late retention but not for acute retention, as previously reported by RG1. The p-maps highlighted the most significant association between dose and acute incontinence in the urethra. Regarding late toxicity outcomes, the most significant regions were located in sub-regions of the bladder specific for each end-point (Figure 1). At a visual comparison, the most significant areas identified by the RG2 pipeline roughly encompassed the clusters identified by RG1 as significantly associated with the same end-points.

Conclusion Variability in VB results could arise from differences in the methods used for statistical analyses, and only a careful standardization of the procedures and sharing of all the relevant information would ensure repeatability of VB results. Here, a first VBA repeatability experiment in RT was performed. However, further in-depth analyses are warranted.

PO-2120 In silico simulation for better prediction of biochemical recurrence in prostate cancer radiotherapy

C. Sosa Marrero 1 , A. Briens 2 , P. Fontaine 1 , O. Acosta 1 , R. de Crevoisier 2,1

1 Univ Rennes, Inserm, LTSI - UMR 1099, Rennes, France; 2 CLCC Eugène Marquis, Radiation Oncology, Rennes, France

Purpose or Objective In prostate cancer radiotherapy, biochemical recurrence has been traditionally predicted from clinical parameters with however limited performance. Mechanistic modelling of tumour growth and response to irradiation allows, through in silico simulation, to better comprehend the response of patients to a given irradiation schedule. The objective of this work was thus to use a simulation marker of our previously developed mechanistic model to obtain better biochemical recurrence predictions. Materials and Methods A cohort of 129 patients from the CLCC Eugène Marquis patients with localised prosate cancer and treated with EBRT was used for this study. Prior to the beginning of treatment, 3 T MRI was performed. Sequences included axial turbo spin echo