ESTRO 2025 - Abstract Book

S2245

Interdisciplinary – Global health

ESTRO 2025

inventoried CO2e contributions, such as patient and staff travel, direct energy consumption and the use of disposables via measurements, counts, queries and questionnaires. We modeled emission reduction for mild and severe hypofractionation for treatments performed on CBCT-guided Linacs over the course of one year at our institution. Reduction scenarios were: courses with 1, 2 or 3 fractions removed and by halving fraction numbers. For these shortened courses we increased dose per fraction and corrected for longer fraction times. Results: For SBRT delivered in, on average, 4.5 fractions of 40 minutes the total treatment emits 172 kg CO2e of which half is associated with preparation. For the fractions, the main contributing factors are 50% direct energy use, of which about half attributable to the Linac (dominated by beam-off energy use), 32% for patient travel and about 9% each for SF6 and staff-travel emissions. For longer series such as 15 x 2.67Gy, the fractions became the dominant factor and patient travel becomes more important, in addition shorter fraction times leading to less direct energy use and attribution of staff and SF6 emissions, see Figure 1. In Table 1 the effect of hypofractionation are shown for short to longer series. A single fraction reduction in the number of fractions resulted in a 4% reduction in total emissions with larger relative reductions for the shorter series. The extreme scenario of halving all series resulted in an overall 32% reduction. A 10% reduction in fractions results in a reduction of 8% similar to 2 fraction reduction over all series. Table 1

Figure 1