Application of the Monaco-serial biological function for cardiac dose constraints in DIBH-IMRT treatment planning for left-sided breast cancer

TL;DR

This study finds the best setting for a Monaco system function to protect the heart during breast cancer radiotherapy.

Contribution

Identifies the optimal K-value range (2≤K≤4) for cardiac dose constraints in DIBH-IMRT using the Monaco-Serial function.

Findings

Group B (K=2-4) achieved optimal heart dose reduction compared to other groups.

Group B maintained target coverage while minimizing cardiac substructure doses.

Anatomical changes from DIBH correlated with improved dose control in Group B.

Abstract

The Serial function in the Monaco treatment planning system is essential for cardiac dose optimization in left breast cancer radiotherapy; however its optimal K-value for deep-inspiration breath-hold intensity-modulated radiotherapy (DIBH-IMRT) has not been established. This study aims to determine the evidence-based K-value configuration for clinical implementation.

41 left breast cancer patients undergoing DIBH-IMRT were retrospectively analyzed. Plans were stratified by Monaco-Serial K-values: Group A (K=1), B (2≤K ≤ 4), and C (K>4). Dosimetric parameters (heart, LAD, Lung-L) and dose-volume reduction rates (Groups B/C vs A) were compared. Correlations between K-values and DIBH-induced anatomical changes (Lung-L volume increment rate, Lung-L/Heart volume ratio, and Heart-Breast Distance increment) were assessed

All plans satisfied target coverage. Group B achieved optimal cardiac protection: mean heart dose (273.9 ± 91.0 cGy), max heart dose (2676.2 ± 1380.7 cGy), and LAD doses (mean: 411.3 cGy; max: 1483.3 ± 736.3 cGy) significantly decreased versus Group A. Lung-L V500cGy in Group B increased marginally but within clinical tolerance. Correlation analysis confirmed that Group B achieved balanced control of mean/maximum heart doses, aligning with the expected effects of anatomical variations induced by the DIBH technique.

Adjusting Monaco-Serial K-value to 2≤K ≤ 4 provides optimal dose constraints for the heart and substructures while ensuring target coverage, making it the optimal parameter setting for left breast cancer DIBH-IMRT.

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