# Robustness of heart dose against cardiac cycle in breast cancer radiotherapy with deep inspiration breath-hold

## TL;DR

This study found that heart radiation doses during breast cancer treatment vary slightly between heartbeats but are still safe using current techniques.

## Contribution

The study quantifies cardiac-phase-dependent dose variations during deep inspiration breath-hold radiotherapy for breast cancer.

## Key findings

- Heart Dmean was 5.10 ± 3.04 Gy in diastole and 5.03 ± 3.05 Gy in systole.
- LMCA Dmean was significantly higher during systole (2.02 ± 0.28 Gy) compared to diastole (1.88 ± 0.23 Gy).
- Current non-ECG-gated DIBH remains adequate for cardiac dose management despite small variations.

## Abstract

This study evaluated dose differences to the heart, left anterior descending coronary artery (LADCA), and left main coronary artery (LMCA) between diastolic and systolic heart phases in radiation therapy for left-sided breast cancer using deep inspiration breath-hold (DIBH). Diastolic and systolic doses to the heart, LADCA, and LMCA were analyzed using electrocardiogram-gated cardiac computed tomography images from 15 women. Radiation therapy plans were created for a total dose of 50 Gy in 25 fractions. Parameters assessed included volume, Dmean, D2%, V5Gy, V10Gy, V20Gy, and V25Gy for the heart; Dmean, D2%, V5Gy, V10Gy, and V20Gy for the LADCA; and Dmean and D2% for the LMCA. The Dmean of the heart was 5.10 ± 3.04 Gy and 5.03 ± 3.05 Gy for diastole and systole, respectively (mean ± 1 standard deviation), and D2% was 37.44 ± 16.03 Gy and 36.15 ± 16.76 Gy. Statistically significant differences were found in the Dmean. LADCA doses showed no significant differences, possibly due to anatomical variations. The Dmean of the LMCA was 1.88 ± 0.23 Gy and 2.02 ± 0.28 Gy for diastole and systole, and D2% was 2.05 ± 0.28 Gy and 2.21 ± 0.30 Gy, with both parameters being statistically significantly higher during systole. Although small, cardiac-phase-dependent dose variations under DIBH were statistically significant, confirming that current non-ECG-gated DIBH remains adequate for cardiac dose management.