ESTRO 2025 - Abstract Book

S411

Clinical - Biomarkers

ESTRO 2025

Purpose/Objective: Improving the prognostic stratification of patients (pts) affected by oligorecurrent hormone-sensitive prostate cancer (orHSPC) and undergoing Stereotactic Body Radiation Therapy (SBRT) is an unmet clinical need. Plasma proteins are promising as minimally invasive prognostic indicators [1-3]. This study aims to evaluate whether a plasma proteomics signature can be identified in these pts and its possible correlation with clinical outcomes. Material/Methods: orHSPC pts with 1-3 nodal and/or bone metastases undergoing SBRT were enrolled (n=35) together with a cohort of healthy donors (HD, n=15). After a median follow up of 25.6 months, two subgroups were identified based on the occurrence of biochemical progression (BP): “no-BP” (n=8, no evidence of BP) and “early-BP” (n=7, BP Free Survival<6 months). Moreover, depending on the occurrence of distant progression (DP), “no-DP” (n=14) and “polymetastatic DP” (n=6) subgroups were indentified. Plasma-EDTA was collected before SBRT. Plasma peptides were separated by liquid chromatography tandem mass spectrometry (LC-MS/MS) based proteomics. Relative protein amount across our samples was determined through label-free quantification (LFQ). The abundance ratio (or fold change, FC) of statistically significant proteins was calculated as the ratio of the average LFQ intensities between the two matched groups.

Results: Plasma protein profiles of orHSPC compared to HD differed in 40 differentially abundant proteins (Figure 1).

Plasma protein profiles of early-BP pts differed from those of no-BP pts in 20 differentially abundant proteins, among which 6 were more abundant in no-BP compared to early-BP (CA1, CDH5, CFHR4, PRDX2, SAA1 and SOD3) (Figure 2).