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The aim of this project is to quantify the carbon footprint of patients within our breast and prostate radiotherapy pathways. In addition, this project will consider the consequence of the COVID-19 pandemic on these emissions as a result of altering our standard procedures. We aim to find carbon footprint hotspots in the patient pathway to highlight where changes are needed. 

To estimate carbon emissions, energy consumption of an Elekta VersaHD linac was recorded for a sample of 4 breast and 6 prostate patients both pre (Jan-Mar 2020) and during COVID-19 (Jan-Mar 2021). An average measurement of the idle power consumption of the linac was also taken. Values for energy consumption due to pre-treatment imaging were also taken into account, using values from literature. Using patient notes, an estimate of travel emissions for pre/post-treatment appointments and treatment fractions was also calculated. All patients were assumed to travel by petrol car with a low fuel economy to provide a worst-case estimate.

Changes to the standard pathway as a result of COVID-19 were incorporated into analysis, including additional appointments for COVID testing, increased number of telephone consultations and changes in fractionation.

Figure 1 shows the linac power consumption for a full course breast IMRT, prostate VMAT and prostate SABR treatments. A reduction in treatment power consumption can be seen due to the reduction in number of breast fractions during COVID-19; however the reverse is seen for prostate VMAT, despite no changes in fractionation. This is likely due to the small sample.

Despite higher power consumption per fraction, the reduced number of fractions used for prostate SABR treatments results in lower overall power relative to prostate VMAT. The power incurred by on-set imaging was negligible with respect to the idle power consumption of a linac and has therefore been ignored for the purpose of these results.

Figure 2 shows the average carbon footprint for each patient pathway. The reduction in fractionation, and therefore the number of appointments, results in a decrease in overall footprint for breast patients during COVID-19. Similarly, the introduction of prostate SABR also leads to an overall reduction in carbon footprint for the prostate pathway.

These preliminary results have demonstrated the environmental impact of patient pathways in radiotherapy, and how a response to COVID-19 has affected this. On-going work will expand this analysis to include more aspects of the patient pathway.