Workflow optimization for robotic stereotactic radiotherapy treatments: Application of Constant Work In Progress workflow☆

Abstract We present an application of the industrial Constant-Work-In-Progress (ConWIP) principle to radiotherapy treatments: from Operations Research to application in practice. Radiotherapy involves a chain of preparation steps before treatment. The time periods between patient referral, initial Computed Tomography (CT) scan, and the treatment should always be as short as possible. This is important in order to not allow further tumor growth and to capture the correct patient anatomy for the treatment. Therefore, the high-in-demand limited machine capacity and scheduling of intermediate steps have to be balanced. Conventionally, the treatment machine calendar is consulted for an open spot and the preparation steps are scheduled around that appointment. Conventional radiotherapy treatment scheduling is efficient in a predictable and low variability environment. Yet it is very inefficient for stereotactic radiotherapy treatments, due to the presence of (a) large variability in preparation time, (b) variable In Room Time especially for liver and lung treatments, which becomes known only right before the treatment, and (c) a high rate of cancellations. The end result is a suboptimal capacity use and high stress load for all personnel. We present a different organization method, a hybrid ConWIP system utilizing standardized work: managing work-in-progress instead of scheduling all steps. Discrete Event Simulations were performed before implementation in order to test the hypothesis and obtain the optimal parameters. Treatment type distribution was as follows: lung (29%), liver (21%), intracranial (13%), head and neck (11%), prostate (7%) and 20% other localizations. Implementation of this ConWIP workflow was supported by workflow software (RT-Flow) combining workflow, prioritization and load balancing. This resulted in a 32% (24%–40%) (95% CI) increase in number of treatments for the CyberKnife ® installation with a negligible increase in time from CT to treatment and an improved stress load for personnel.