Abstract
Purpose
Dose to the left anterior descending artery (LAD) may be significant in patients receiving
left-sided irradiation for breast cancer. We investigated if prospective contouring
and avoidance of the LAD during treatment planning were associated with lower LAD
dose.
Methods and Materials
We reviewed dosimetric plans for 323 patients who received left whole breast or chest
wall irradiation with or without internal mammary node (IMLN) coverage between 1/2014
and 1/2019 at a single institution. The LAD was contoured prospectively for 155 cases,
and techniques were utilized to minimize LAD dose. Dose-volume-histograms from these
patients were compared to those of 168 patients for whom the LAD was contoured retrospectively
after treatment completion. EQD2 was calculated to account for fractionation differences.
Results
Compared to cases where the LAD was contoured retrospectively (n = 126), prospective LAD contouring (n = 124) was associated with lower unadjusted median max and mean LAD doses for 250
patients receiving whole-breast irradiation (WBI) without IMLN coverage: 8.5 Gy vs 5.2 Gy (p < 0.0001) and 3.6 Gy vs 2.7 Gy (p < 0.0001), respectively. EQD2 median max and mean LAD doses were also lower with
prospective LAD contouring: 5.2 Gy vs 3.0 Gy (p < 0.0001) and 1.9 Gy vs 1.5 Gy (p < 0.0001), respectively. Compared to cases where the LAD was contoured retrospectively
(n = 42), prospective LAD contouring (n = 31) was associated with lower max LAD doses for 73 patients with IMLN coverage:
20.4 Gy vs 14.3 Gy (p = 0.042). There was a nonsignificant reduction in median mean LAD dose: 6.2 Gy vs 6.1 Gy (p = 0.33). LAD doses were reduced while maintaining IMLN coverage (mean V90%Rx >90%).
Conclusions
Prospective contouring and avoidance of the LAD were associated with lower max and
mean LAD doses in patients receiving WBI and with lower max LAD doses in patients
receiving IMLN treatment. Further reduction in LAD dose may require stricter optimization
weighting or compromise in IMLN coverage.
Keywords
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Article info
Publication history
Published online: August 30, 2020
Accepted:
July 14,
2020
Received in revised form:
June 29,
2020
Received:
March 6,
2020
Footnotes
The author(s) claim no conflicts of interest related to the work as described herein.
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Identification
Copyright
© 2020 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
