# Comparative dosimetric analysis of deep inspiration breath-hold versus free breathing radiotherapy in lung cancer: special emphasis on cardiac and subcardiac structure protection

## TL;DR

This study compares deep inspiration breath-hold and free breathing radiotherapy in lung cancer, showing that breath-hold reduces radiation exposure to the heart and lungs.

## Contribution

The study demonstrates that DIBH provides consistent dosimetric benefits in lung cancer radiotherapy, particularly for cardiac substructures.

## Key findings

- DIBH significantly reduces mean lung dose and V20Gy compared to free breathing.
- DIBH lowers cardiac doses, including D2% and V45Gy, and benefits subcardiac structures like the LAD.
- Dosimetric advantages are consistent across tumor laterality and subcarinal lymph node involvement.

## Abstract

•Cardiac dose burden correlates with adverse cardiac events in lung cancer patients.•DIBH offers consistent dosimetric benefit in pulmonary and cardiac metrics.•The extent of dosimetric change depends on tumor site and lymph node involvement.•In complex cases (e.g. subcarinal lymph nodes) DIBH shows greater dosimetric benefit.•Dose reduction in cardiac substructures might reduce the risk of toxicities.

Cardiac dose burden correlates with adverse cardiac events in lung cancer patients.

DIBH offers consistent dosimetric benefit in pulmonary and cardiac metrics.

The extent of dosimetric change depends on tumor site and lymph node involvement.

In complex cases (e.g. subcarinal lymph nodes) DIBH shows greater dosimetric benefit.

Dose reduction in cardiac substructures might reduce the risk of toxicities.

Radiation therapy (RT) plays a central role in the treatment of lung cancer. However, cardiac and pulmonary toxicities remain major concerns. Deep inspiration breath-hold (DIBH) has been shown to improve target stability and reduce organ-at-risk (OAR) exposure, but data in lung cancer, particularly regarding cardiac substructures, remain limited.

We retrospectively analysed 32 patients with lung cancer treated with RT at our institution between 2020 and 2021. Each patient underwent planning CTs in both DIBH and free breathing (FB), generating a total of 64 treatment plans using VMAT (60 Gy in 30 fractions). Contouring followed ESTRO ACROP guidelines, including detailed segmentation of cardiac chambers and coronary arteries. Dosimetric endpoints included Dmean, D2%, and VxGy for lung, heart, and subcardiac structures. Statistical comparisons between DIBH and FB plans were performed.

DIBH significantly increased lung volume and improved all lung dosimetric parameters, including Dmean (13.13 vs. 14.49 Gy, p < 0.001) and V20Gy (24.37 % vs. 27.28 %, p < 0.001). Cardiac sparing was evident, with lower heart D2% (39.91 vs. 41.67 Gy, p = 0.012) and V45Gy (2.23 % vs. 2.53 %, p = 0.005). Notably, significant reductions were observed in the LAD (Dmean: 5.59 vs. 6.57 Gy, p = 0.004), LCX, and LV. Subgroup analyses demonstrated consistent dosimetric advantages across tumor laterality and level 7 nodal involvement.

DIBH offers substantial and consistent dosimetric benefits in lung cancer RT, reducing radiation burden to pulmonary, cardiac, and coronary structures. Given the known association between cardiac dose and long-term morbidity, these findings support the broader implementation of DIBH, especially in anatomically challenging cases involving subcarinal nodes or left-sided tumors.