ESTRO 2025 - Abstract Book

S3972

Radiobiology - Tumour radiobiology

ESTRO 2025

Results:

Labelling of the treatment naïve cohort highlighted the high level of molecular intratumoral heterogeneity of PDAC regarding molecular subtypes, including within a single duct. After FFX alone, a shift was visually observed towards the BLP, whereas tumors treated with FFX + SBRT displayed a more enhanced CLP profile. After ductal quantification, tumors treated with FFX + SBRT were significantly associated with more Classical and less Basal-like cells than the tumors treated with FFX alone or treatment-naïve. Similarly, a nearly significant trend in decreased level of KRT17 + cells, a marker associated with Basal-like and poor prognosis, was identified in the FFX + SBRT cohort compared to FFX alone. (Figure 2) Conclusion: We successfully applied a practical multiplex staining-based classifier allowing to easily display the molecular hetereogeneity of PDAC, including at the intraductal level. Contrary to the non-treated and FFX cohorts, tumors treated with FFX + SBRT were significantly enriched in cells displaying a Classical subtype, associated with a better prognosis, suggesting either a selection or a reprogramming effect of SBRT on the Basal-like cells.