ESTRO 2023 - Abstract Book

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ESTRO 2023

Nine patients were included. On average more radiation-induced apoptosis was found in HPV-positive compared to HPV- negative OPSCC patients at 5d (Fig 1), which indicates that apoptosis at 5d is related to expected radiosensitivity differences. Neither apoptosis nor DNA repair kinetics at 24h correlated strongly with apoptosis at 5d (p>0.05) (Fig 2).

Conclusion Residual DNA damage did not correlate to more apoptosis; therefore, residual DNA damage might not be suitable to predict radiosensitivity. Moreover 24h after treatment appears to be too early to measure radiation-induced apoptosis, as absolute apoptosis at 24 hours was low and did not correlate to apoptosis at 5d. Apoptosis at 5d, however, did reflect the radiosensitivity differences that were expected based on HPV status. 1 ME Capala (2021) Oral Oncology 2 I Lauwers (2022) ESTRO 3 KK Ang (2010) New England Journal of Medicine

PO-2232 Prediction of clonogenic survival following spatial fractionation - a novel 2D quadrat analysis

D. Arous 1 , J. Larsen Lie 2 , N. Frederike Jeppesen Edin 3 , E. Malinen 2

1 Oslo University Hospital, Department of Medical Physics, Oslo, Norway; 2 University of Oslo, Department of Physics, Oslo, Norway; 3 University of Oslo , Department of Physics, Oslo, Norway