Time Trends in Cardiac Doses in 10,000 Patients Receiving Curative Thoracic Radiation Therapy Between 2009 and 2020.

Aims

Cardiac exposure to radiation is associated with an increased risk of cardiovascular morbidity. Radiation therapy technologies have developed to provide target dose coverage with less exposure to adjacent organs. We investigated trends in cardiac exposure among patients treated with curative-intent radiotherapy from a single institution.

Materials And Methods

A total of 10,215 treatment courses were analyzed from 9,966 patients treated for intrathoracic or breast cancers in 2009-2020. Hearts were redelineated using an artificial intelligence model to ensure consistency. Cardiac doses were extracted in 3D and converted, voxel-by-voxel, to equi-effective doses in 2 Gy fractions (EQD2) using α/β = 2 Gy. The mean heart dose (in EQD2) and volume exposed to 5 and 40 Gy, respectively, were extracted. Time trends were investigated for each diagnosis.

Results

Patients with esophageal cancer had the highest mean heart dose (median = 11.67 Gy; IQR = 2.85-18.18), while patients treated for right-sided breast cancer (median = 0.34 Gy; IQR = 0.21-0.51) and lymphoma (median = 0.01 Gy; IQR = 0.00-0.38) had the lowest. A decreasing trend over time was seen most clearly for patients with esophageal and lung cancers (P < .05). For left-sided/bilateral breast cancer, volume exposed to 5 Gy increased over time (P = .032).

Conclusion

Radiation exposure to the heart decreased significantly in patients treated between 2009 and 2020, likely due to increased awareness of cardiovascular toxicity and technological developments. For left-sided/bilateral breast cancer, V5 increased significantly, possibly related to increased prioritization of target coverage.