ESTRO 2024 - Abstract Book

S786

Clinical - CNS

ESTRO 2024

this definition, 35 (15%) patients developed RN with an actuarial risk of 35% and 38% at 1 and 2 years, respectively. An OS of 9 months (95% CI 8-11) was found.

Figure 1. The predicted (the error bars represent 95% confidence intervals) and observed RN probability for the single fraction group (N=162). Patients were diagnosed according to the definition of (asymptomatic and symptomatic) RN based on progression from nadir.

Figure 2. The predicted (the error bars represent 95% confidence intervals) and observed RN probability for the single fraction group (N=162). Patients were diagnosed according to the definition of (asymptomatic and symptomatic) RN based on progression from baseline.

Conclusion:

For the first time, the NTCP prediction model for RN has been externally validated. This study has shown that the accuracy of the NTCP model depends on which definition to diagnose RN is chosen. This finding emphasizes the importance of establishing a unanimously accepted and accurate definition of RN for use in future studies related to SRT and when informing the patient about complication risks. The definition of ‘RN diagnosis based on