Purpose/Objective: In order to preserve the patient's cardiac integrity, a good practice that would be simple and quick to implement would be to optimize dose on the left anterior descending coronary artery (LADCA) during dosimetric planning treatment. However, manual delineation of LADCA remains complicated to perform in clinical routine on non-injected CT-scans. To conclude on the feasibility of such a practice, we investigated the automatic delineation robustness of the Mirada software (Mirada Medical, UK) to generate these volumes. Materials/methods: Forty randomly selected CT-scans of breast cancer patients were used. All were delineated by a radiation therapist following international recommendations (Duane et al., 2017). A planning organ at risk volume (PRV) with a 10 mm margin centered on the LADCA was also performed. Among the forty CT-scans, twenty were used to develop the automatic segmentation atlas using “Workflow Box” auto-segmentation algorithm. The remaining twenty other CT-scans were compiled on the software in order to obtain auto-segmented structures. The relevance of the contours was carried out with the Artiview software (Aquilab, Loos-lès-Lille, France) in order to determine both Dice-similarity coefficients (DSC) and Jaccard indexes. Finally, dosimetric planning treatment in volumetric modulated arc therapy conditions was performed using Eclipse treatment planning system (Varian). Results: Because of variability, both in terms of shape and spatial localization, the atlas-based auto-segmentation software did not succeed in LADCA delineation. Then, LADCA contours were not available for DSC and Jaccard indexes assessment. On the other hand, the use of margins on the LADCA made it possible to create such an Atlas. The average DSC is 0.36 ± 0.15 and the Jaccard index reaches 0.23 ± 0.11. The results associated with dosimetry planning treatment are presented in Table 1.

The use of a PRV instead of the LADCA contour tends to overestimate the maximum doses by around 30%. However, the mean and median doses are of the same order of magnitude. Conclusion: Small volume structures do not allow the creation of a robust contouring atlas. However, to overcome this limitation, the use of margins to define a PRV has been quite effective. However, it overestimates the maximum doses by about 30%, so the constraints used to limit doses to the coronary arteries during treatment planning will have to be adjusted in this way.

Table 1 Dosimetric results from VMAT optimization for breast radiotherapy treatments.

Left breastRight breast
PRVLADCAPRVLADCA
Average dose (Gy) 12.71 ± 6.54 13.24 ± 7.48 5.86 ± 1.34 5.61 ± 1.39 
Median Dose (Gy) 11.75 ± 6.57 13.32 ± 8.33 5.75 ± 1.32 5.59 ± 1.27 
Maximum dose (Gy) 33.29 ± 12.85 25.28 ± 11.18 10.25 ± 1.96 7.99 ± 2.09 
Left breastRight breast
PRVLADCAPRVLADCA
Average dose (Gy) 12.71 ± 6.54 13.24 ± 7.48 5.86 ± 1.34 5.61 ± 1.39 
Median Dose (Gy) 11.75 ± 6.57 13.32 ± 8.33 5.75 ± 1.32 5.59 ± 1.27 
Maximum dose (Gy) 33.29 ± 12.85 25.28 ± 11.18 10.25 ± 1.96 7.99 ± 2.09 

Citation Format: Nicolas Tkatchenko, Pierre Loap, Eliot Nicolas, Youlia Kirova. Evaluation of workflow box mirada software for automatic delineation of left anterior descending coronary artery (LADCA) in order reduce cardiac toxicity for radiotherapy breast cancer treatments [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-16.