ESTRO 2025 - Abstract Book

S608

Clinical - Breast

ESTRO 2025

Results: The results are summarized in Tab 1.

In all cases the extracted DNA concentration was in the range of 0.5-1.5 ng/ul indicating a suboptimal quantity of genomic material. According to manufacturer guidelines, a DIN score greater than 3 is required for next-generation sequencing (NGS), but nine samples failed to meet this threshold. On the other hand, two samples had a DIN <3, and two had a DIN >3. Six samples exhibited γH2A.X foci, while two samples displayed 53BP1 foci without concurrent γH2A.X expression. Only one sample showed both γH2A.X and 53BP1 foci. Conclusion: Conventional and additional IHC analyses did not reveal unexpected alterations. However, the observed high levels of DNA fragmentation and low residual DNA concentration suggest significant radiotherapy-induced DNA damage. The presence of γH2A.X foci in some samples is consistent with genomic instability. The detection of 53BP1 foci without γH2A.X expression may imply the activation of alternative, γH2A.X-independent DNA repair pathways. Notably, one sample showed both γH2A.X and 53BP1 foci, suggesting the activation of non-homologous end-joining (NHEJ) repair mechanisms, potentially with suppression of homologous recombination. Expanding this study and further exploring these findings could shed light on novel diagnostic and therapeutic strategies for early-stage breast cancer.

Keywords: DNA repair, preoperative radiotherapy

References: 1.

doi:10.1093/ajcp/aqad046

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doi:10.1186/1748-717X-8-98