How Much Can Optimization of Hypofractionation Help to Reduce Carbon Equivalent Emissions? A Single-Center Modeling...

Climate change poses a major threat to public health. The health care sector paradoxically contributes significantly to greenhouse gas emissions. In radiation therapy, increased hypofractionation could reduce both patient transport and linear accelerator (LINAC) use, but the size of the impact remains largely undocumented. We estimated department-wide CO₂ equivalent (CO₂e) emissions of patient transport and LINAC energy consumption both in a real-world scenario and in a hypothetical maximized hypofractionation scenario.

We performed a retrospective exploratory study of all patients treated with external beam radiation therapy in 2019 (pre-COVID-19 year) at the University Hospitals Leuven (Belgium). CO₂e emissions of patient transport were modeled by considering the kilometers traveled by car between the patient's home and the hospital as well as the number of visits necessary for the treatment. Second, the hypothetical impact of implementing the most hypofractionated schedules according to the current (December 2024) best scientific evidence was calculated using the model. Finally, energy consumption of our Varian TrueBeam and Halcyon LINAC was measured to calculate the related CO₂e emissions.

In 2019, there were 43,433 patient visits over 2625 external beam radiation therapy courses with an estimated total of 2.67 million km traveled, resulting in an estimated 394 t of CO₂e emissions. Implementation of hypothetical maximalized hypofractionation would decrease emissions by 18.3% (95% CI, 17.7%-20.0%) on average. The reduction was much larger for early breast cancer (-32.4%) and prostate cancer (-48.5%) than for all the other pathologies (-7.0%). Comparing a prostate treatment in 16 (n = 2 patients) and 5 (n = 2) fractions on the TrueBeam and 16 (n = 2) fractions on the Halcyon, energy use was, respectively, 47.1, 23.6, and 9.2 kWh over the total course, or 6.17, 3.10, and 1.21 kg of CO₂e emissions.

In our hypothetical scenario, maximal optimization of hypofractionation schedules significantly reduces CO₂e emissions by decreasing patient transport and, to a much lesser extent, energy consumption.