Internal mammary node irradiation using an 8-field IMRT technique significantly increased mean heart dose and exposure to critical cardiac substructures in left-sided breast cancer.
Observational (n=20)
No
Does internal mammary lymph node inclusion increase radiation dose to cardiac substructures in breast cancer patients undergoing postoperative breast-conserving radiotherapy?
Inclusion of internal mammary lymph nodes in left-sided breast cancer radiotherapy significantly increases radiation exposure to critical cardiac substructures, emphasizing the need for substructure-sparing planning to mitigate long-term cardiotoxicity.
Absolute Event Rate: 775.26% vs 738.17%
p-value: p=0.042
Objective: To evaluate the dosimetric impact of internal mammary lymph node (IMN) inclusion versus exclusion (non-IMN) on cardiac substructures in postoperative breast-conserving radiotherapy, providing evidence-based insights for clinical decision-making. Methods: This study included 20 breast cancer patients (10 on the left and 10 on the right) who had previously received radiotherapy in our hospital after breast conserving surgery. The clinical target volume (CTV) encompassed the ipsilateral breast, supraclavicular lymph nodes, and internal mammary lymph nodes (IMNs). Organs at risk (OARs) comprised the heart and its substructures-including the left ventricle (LV), left atrium (LA), right ventricle (RV), right atrium (RA), anterior myocardial territory (AMT), left anterior descending artery (LAD), left circumflex artery, and right coronary artery-as well as bilateral lungs, ipsilateral/contralateral lungs, contralateral breast, thyroid, and spinal cord. For both target delineation strategies, treatment planning utilized 8-field fixed-beam intensity-modulated radiation therapy (IMRT) with 6 MV X-rays, delivering 50 Gy in 25 fractions over 5 weeks to 95% of the planning target volume (PTV). Continuous variables were reported as mean ± standard deviation (SD). Normality was assessed using Shapiro-Wilk tests, with paired t-tests applied for normally distributed data and Wilcoxon signed-rank tests for non-parametric comparisons. Statistical significance was defined as P0.05) or left anterior descending artery (LAD) dose exposure. These findings suggest that clinical decision-making should carefully weigh the competing risks of locoregional recurrence against potential cardiotoxicity, with consideration given to advanced radiotherapy techniques for cardiac dose optimization when treating left-sided malignancies. 2. Current evaluation metrics for breast cancer radiotherapy planning, predominantly focused on mean heart dose and low-dose volume parameters, may not sufficiently capture the risk of radiation-induced cardiac toxicity. Comprehensive dosimetric assessment requires delineation of cardiac substructures (e.g., ventricles, coronary arteries) as discrete organs-at-risk (OARs), with their dose constraints systematically integrated into plan optimization and quality assurance protocols. This paradigm shift toward substructure-sparing approaches could enhance the therapeutic ratio by minimizing late cardiovascular complications while maintaining target coverage. 3. Postoperative breast-conserving radiotherapy should follow guideline recommendations regarding IMN irradiation strictly.
Xie et al. (Tue,) conducted a observational in Breast cancer (n=20). 8-field IMRT with internal mammary lymph node (IMN) irradiation vs. 8-field IMRT without IMN irradiation was evaluated on Mean heart dose (Dmean) in left-sided breast cancer (p=0.042). Internal mammary node irradiation using an 8-field IMRT technique significantly increased mean heart dose and exposure to critical cardiac substructures in left-sided breast cancer.