Analysis of coronary artery dosimetry in the 3-dimensional era: Implications for organ-at-risk segmentation and dose tolerances in left-sided tangential breast radiation.

PURPOSE

To evaluate the dose to the left anterior descending artery in patients receiving left-sided tangential breast radiation.

METHODS AND MATERIALS

The study cohort consisted of 50 left-sided breast cancer patients who were sequentially simulated at our institution. The heart and left anterior descending (LAD) artery were contoured from its origin on the left main coronary artery down to the last visible segment of the vessel. Detailed dosimetry of the heart and LAD artery were obtained and analyzed.

RESULTS

Excellent correlation between the dose to the heart and LAD artery was discovered. The mean LAD dose was 17.98 Gy. The mean dose to the proximal LAD was 2.46 Gy. The median V25 was 2.91% and the mean heart dose 3.10 Gy. For every 100 cGy increase in mean heart dose, mean LAD dose increased by 4.82 Gy. For every percent increase in the heart V10 and V25, there was a 2.23 Gy and 2.77 Gy increase in mean LAD dose, respectively. For every percent increase of heart V25, a 5.6% increase in the LAD V20 was demonstrated.

CONCLUSIONS

The LAD artery dose correlates very closely with all of the commonly measured heart dose constraints, and does not need to be contoured separately when standard tangential borders are used. Incidental LAD artery doses remain with supine breast tangential radiation therapy.