KEY POINTS
- This retrospective pilot study evaluated 100 patients receiving curative prostate radiotherapy on the same Varian Trilogy linear accelerator: 50 received 26 fractions, and 50 received five fractions. Each group intentionally included 25 patients from Lombardy and 25 from other Italian regions.
- Median estimated carbon emissions were 972.55 kgCO₂e for the 26-fraction schedule and 402.85 kgCO₂e for five fractions, representing a 58.6% reduction with extreme hypofractionation (p < 0.00001).
- Patient travel was the dominant contributor, accounting for 81.3% of emissions with 26 fractions and 91.6% with five fractions. Median travel-related emissions were 655.85 versus 335.09 kgCO₂e, respectively (p = 0.00782).
- Estimated building-related emissions were 144.7 versus 27.8 kgCO₂e per treatment course, while accelerator construction and maintenance contributed 125.1 versus 24.1 kgCO₂e with 26 and five fractions.
- Linear-accelerator energy use during treatment contributed comparatively little: median emissions were 9.79 kgCO₂e with 26 fractions and 3.08 kgCO₂e with five. Beam-on and idle consumption together represented less than 2% of total emissions.
- Building electricity use could not be measured directly and was estimated using a machine-learning model trained on commercial-building data. The final model achieved an R² of 0.728 and predicted annual departmental electricity consumption of 790 MWh.
- Travel calculations assumed a medium petrol car and used standardized rules for temporary accommodation based on distance. Staff travel, building construction and several imaging and equipment-related sources were excluded, limiting the reliability of absolute carbon-footprint estimates.
CLINICAL TAKEAWAY
When five-fraction prostate radiotherapy is already oncologically appropriate, reducing treatment visits may also substantially reduce environmental and patient travel burdens. Environmental considerations should support, not determine, fractionation choice: this was a small modelling study rather than a clinical comparison, and most of the estimated benefit depended on assumed travel patterns.