Robust optimization of a radiotherapy pretreatment preparation workflow.

Objective: Increasing cancer incidence, staff shortage and high burnout rate among radiation oncologists, medical physicists and radiation technicians is putting many departments under strain. Operations research (OR) tools could optimize radiotherapy processes, however, clinical implementation of OR-tools in radiotherapy is scarce since most investigated optimization methods lack robustness against patient-to-patient variation in duration of tasks. By combining OR-tools, a method was developed that optimized deployment of radiotherapy resources by generating robust pretreatment preparation schedules that balance the expected average patient preparation time ( F mean ) with the risk of working overtime ( RoO ). The method was evaluated for various settings of a one-stop shop (OSS) outpatient clinic for palliative radiotherapy.
 Approach: The OSS at our institute sees, scans and treats 3 to 5 patients within one day. The OSS pretreatment preparation workflow consists of a fixed sequence of tasks, which was manually optimized for radiation oncologist and CT availability. To find more optimal sequences, with shorter F mean and lower RoO , a genetic algorithm was developed which regards these sequences as DNA-strands. The genetic algorithm applied natural selection principles to produce new sequences. A decoder translated sequences to schedules to find the conflicting fitness parameters F mean and RoO . For every generation, fitness of sequences was determined by the distance to the estimated Pareto front of F mean and RoO . Experiments were run in various OSS-settings.
 Main results: According to our approach, the expected F mean of the current clinical schedule could be reduced with 37%, without increasing RoO . Additional experiments provided insights in trade-off between F mean , RoO , working shift length, number of patients treated on a single day and staff composition.
 Significance: Our approach demonstrated that OR-tools could optimize radiotherapy resources by robust pretreatment workflow scheduling. The results strongly support further exploration of scheduling optimization for treatment preparation also outside a one-stop shop or radiotherapy setting.