ESTRO 2023 - Abstract Book

S1857

Digital Posters

ESTRO 2023

the one standard deviation regression uncertainty of the measured slope was estimated. The individual slope uncertainties were combined using the root of mean squares (RMS) of the individual patient values. This value was compared to the observed cohort variation. Results In mean, the normalized ADC_GTV increased by 14.8 % (SD: 39.3 %) between fraction one and five, while ADC_kidney decreased by 0.8 % (SD: 12.4 %) (Figure 1). The ADC_GTV slopes varied between patients and had a standard deviation of 0.08 (Figure 2). In comparison, the RMS of the individual slopes was smaller (0.04), indicating that the ADC slopes can potentially be used for patient stratification.

Conclusion Longitudinal ADC of pancreatic tumours has potential to detect relevant patient-specific biological changes during RT. This might be used for response assessment and patient stratification. Further evaluation is needed to determine if changes can be captured early in the treatment course, and to establish correlation to outcome.