Dosimetric impact of sparing base of heart on organ at risk doses during lung radiotherapy

Abstract

Background

Minimising heart exposure during lung radiotherapy (RT) is important due to association between increased cardiac dose and adverse outcomes such as cardiac toxicity and reduced overall survival. This study evaluated the impact of incorporating a cardiac avoidance area (CAA) located at the base of the heart on the dose received by cardiac subregions and thoracic organs at risk.

Methods

A comparative analysis was conducted on patients treated with lung RT at a single centre before and after the CAA was introduced as an anatomical region at risk (ARR) in April 2023. Two patient cohorts were analysed: those treated prior to CAA implementation (April 2021-March 2023, 923 patients) and those treated post implementation (April 2023-March 2024, 477 patients). For the second group, plans were optimised to keep CAA maximum dose to 1 cc below 19.5  Gy in 20 fractions (or equivalent biologically effective dose). Key dose metrics for the CAA, heart, lungs, oesophagus, and spinal canal were compared between the cohorts.

Results

The introduction of the CAA as an ARR resulted in significant reductions in CAA and overall heart dose, with median CAA maximum dose (EQD2) decreasing from 32.0  Gy₃ to 16.9  Gy₃ (p < 0.001). No significant increases in dose were observed for other thoracic organs at risk.

Conclusions

Implementing a cardiac avoidance area in lung RT planning significantly reduces doses to critical heart regions without compromising the safety of other organs. This approach holds promise for reducing cardiac-related adverse events and improving overall survival in patients with lung cancer undergoing RT.