Estimating Carbon Dioxide Emissions and Direct Power Consumption of Linear Accelerator–Based External Beam Radiation Therapy
R.F. Shenker, Timothy Johnson, Márcio Garcia Ribeiro, Anna Rodrigues, Junzo Chino
Abstract
IntroductionClimate change is one of the most dire health threats that humanity faces. We aim to estimate the CO2 emissions associated with the energy usage from LINAC based external beam radiotherapy (EBRT) for the most common cancer diagnoses.Materials and MethodsWe identified patients with four most common cancer types treated with curative intent EBRT. Beam-on time for each fraction was extracted from the treatment planning system and averaged over each site and treatment modality. The power was multiplied by the beam on time in hours to yield kWh. Using the US Environmental Protection Agency (EPA) Greenhouse Gas Equivalencies calculator, the kWh was converted into estimates of CO2 equivalent emissions for the average U.S. power grid. Idle time of the LINAC was estimated via Varian Medical Systems.ResultsA total of 10 patients were included for each of the following modalities: conventionally fractionated for prostate cancer (28 fractions [fx]), prostate stereotactic body radiotherapy (SBRT) (5 fx), 15 and 5 fx regimens for early-stage breast cancer, 3 and 5 fx SBRT regimens for early stage lung cancer, conventional EBRT (30 fx) for locally advanced lung cancer, and short (5 fx) and long course (25-28 fx) for rectal cancer. The modality with the lowest and highest carbon emissions per course, on average, is prostate SBRT (2.18 kg CO2, IQR 1.92 – 2.30) and conventional treatment for prostate cancer (17.34 kg CO2, IQR 10.26 – 23.79), respectively. This corresponds to CO2 equivalent emissions of driving average 5.4 miles and 41.2 miles in a standard vehicle, respectively. “Standby” mode for a LINAC Truebeam and Clinac IX uses 112 kW-hr and 64.8 kW-hr per day.ConclusionWe have estimated CO2 emissions arising from direct energy usage of a LINAC for four common cancers treated with EBRT. “Standby” mode of a LINAC uses the most energy per day. Comprehensive studies are warranted to minimize the environmental impacts of health and cancer care.