ESTRO 2025 - Abstract Book

S2313

Interdisciplinary – Health economics & health services research

ESTRO 2025

3297

Digital Poster Capacity-limited triage in proton therapy: a ΔNTCP prioritised waiting list to optimise capacity utilisation and ΔNTCP gain Eva M. Negenman 1,2 , Koen F. Crama 3,4 , Frank J.W.M. Dankers 3 , Mischa S. Hoogeman 1,2 , Steven J.M. Habraken 3,2 1 Department of Radiotherapy, Erasmus MC Cancer Institute, Rotterdam, Netherlands. 2 Department of Medical Physics & Informatics, Holland PTC, Delft, Netherlands. 3 Department of Radiation Oncology, Leiden University Medical Center, Leiden, Netherlands. 4 Radiotherapy, Holland PTC, Delft, Netherlands Purpose/Objective: With increasing cancer incidence and limited proton therapy capacity, challenges arise in patient selection for proton therapy. In the Netherlands, head-and-neck (HNC) patients are selected for proton therapy based on modelled differences in normal tissue complication probability (ΔNTCP) between photon and proton therapy, with patients above a ΔNTCP threshold qualifying. However, the first-come, first-served implementation, combined with fluctuations in patient supply and capacity, may exclude patients who would benefit substantially from proton therapy and leave capacity unused, while DL prediction models enable ΔNTCP early in the process. We investigate a prioritised waiting list model to optimise capacity utilisation and ΔNTCP gains. Material/Methods: Our model adds new patients p in week_n with positive plan comparisons (ΔNTCP grade II ≥ 10% or ΔNTCP grade III ≥ 5% [1]) to a waiting list (Figure 1). Patients are prioritised based on their ΔNTCP, with grade III toxicities weighted twice as heavily as grade II: Patients whose position falls within the available slots for week_n are referred for proton therapy. Patients not referred remain on the waiting list and will be considered again the following week. However, patients who exceed the max_waiting_time or whose position exceeds the max_waitinglist_length are referred for photon therapy. In our simulation, the capacity was defined as c = 1 + E , where follows from a Poisson distribution (µ E =1). The weekly patient supply p also followed a Poisson distribution (µ p =5). We evaluated the effect of max_waitinglist_time (1-12 weeks) on ΔNTCP and capacity utilization, while max_waitinglist_length was limited to 5 patients. OAR values and baseline toxicities were independently sampled from 151 positive and 164 negative HNC patients treated at our center and used to calculate ΔNTCPs.