ESTRO 2024 - Abstract Book

S5363

Radiobiology - Tumour biology

ESTRO 2024

At 2-weeks post-RT 8/10 patients had evaluable changes in apparent diffusion coefficient (ADC) on MRI with half of these having an increase in ADC of >50% suggesting early treatment response 4 . 2/4 ADC responders went on to have a CR at 12-months post-RT and the remaining a partial response (PR). Overall, at 12M 5 patients achieved CR, 3 PR and 2 had died. Analysis for DEGs in the complete vs partial responders post-RT samples found 7 significantly upregulated genes in the responders (L2Fc>4, adj.p value<0.05) of which 4 were related to immune response, encoding genes related to immunoglobulins (IGLV3-10/IGLC7) and neutrophil activation (CD177). SRUS was performed on 4 patients with 3/4 patients having a significant reduction in both mean vessel density and vessel diameter at 2-weeks post-RT. The histopathology corroborates this showing a reduction in mean vessel count in all these patients and visually smaller vessel lumens (Fig.2). All patients with a reduction in vessel density and diameter on SRUS at 2-weeks post-RT went on to have a CR on MRI at 12-months and the other showed only a PR.

Conclusion:

Preliminary analysis has shown interesting associations between radiation response and angiogenesis and immune/inflammatory pathways. Our findings also suggest that early microvasculature changes seen on SRUS after RT have the potential to predict long-term response. Work is ongoing to investigate this in a larger cohort (as trial