Quantifying the Carbon Footprint of External Beam Radiation Therapy-A Narrative Review

The health care sector contributes significant amounts of greenhouse gases (GHGs) to the global climate change issue. However, little remains known about the specific contribution of radiation therapy even though there are methods/tools to quantify its carbon footprint. This narrative review aimed to identify aspects within the external beam radiation therapy pathway that are associated with a significant carbon footprint and the methods by which this footprint can be assessed. These were categorised as power consumption of magnetic resonance imaging (MRI) and computed tomography (CT) for imaging and/or diagnosis in the pre-treatment setting, power consumption of linear accelerators (LINACs) in the treatment phase as well as patient travel. A search strategy with appropriate search terms was carried out on PubMed, Scopus, Embase and Web of Science to identify relevant studies. No time filter was applied during the search. Life cycle assessment as a method to quantify carbon footprint for radiation therapy remains under-utilised. Direct conversion of power consumption into carbon dioxide equivalence is a more feasible method. In the pre-treatment setting, use of MRI results in more GHG output compared to CT. Longer courses of radiation therapy result in significantly more GHG output compared to shorter fractionations as an alternative in the same disease site. Fractionation impacts the frequency of patient travel, another aspect that contributes significantly to the radiation therapy carbon footprint. Identification of areas contributing the most to the carbon footprint of radiation therapy will pave the way for future research into finding solutions to its offset.