Evaluating the environmental Effects of Simulation-Free radiation therapy for palliative treatments.

Abstract

This study evaluated the environmental impact of simulation-free (Sim-free) radiation treatment workflow for single-fraction palliative radiation treatments, comparing operational expenditures (OpEx) and capital expenditures (CapEx). We compared 16 patients treated with Sim-free RT to 16 patients treated with a conventional workflow. Carbon dioxide equivalent (CO2e) emissions were calculated for OpEx (patient travel, energy consumption of LINAC and CT-simulation, building air-conditioning) and CapEx (embodied carbon of equipment manufacturing, maintenance, and bunker construction amortized over usage time). Sensitivity analyses were performed on patient travel distances and LINAC occupancy times. In terms of OpEx, the Sim-free workflow reduced emissions by 58% compared to the conventional workflow (10.3 kg CO2e vs. 24.6 kg CO2e per patient), primarily driven by the elimination of a round-trip for CT simulation. However, when including CapEx, the Sim-free workflow resulted in higher total emissions (82.4 kg CO2e vs. 49.3 kg CO2e per patient) due to the increased LINAC occupancy time (45 vs. 15 min). Sensitivity analysis demonstrated that if Sim-free LINAC time is reduced to 20-25 min, the total carbon footprint becomes equivalent to or lower than the conventional workflow. Sim-free RT significantly reduces the operational carbon footprint and patient travel burden. However, manufacturing and maintenance of LINACs are carbon costly. Current Sim-free efficiencies (45-minute slots) result in a higher total carbon cost than the conventional workflow. Optimizing the workflow to reduce LINAC occupancy is the key metric to making Sim-free RT the superior environmental choice overall.