Current Cardioprotective Strategies for the Prevention of Radiation-Induced Cardiotoxicity in Left-Sided Breast Cancer Patients

Laterality of Radiation Therapy in Breast Cancer is Not Associated With Increased Risk of Coronary Artery Disease in the Contemporary Era

Purpose

External beam radiation therapy (EBRT) is a critical component of breast cancer (BC) therapy. Given the improvement in technology in the contemporary era, we hypothesized that there is no difference in the development of or worsening of existing coronary artery disease (CAD) in patients with BC receiving left versus right-sided radiation.

Methods and Materials

For the meta-analysis portion of our study, we searched PubMed, Web of Science, and Scopus and included studies from January 1999 to September 2022. CAD was identified using a homogenous metric across multiple studies included. We computed the risk ratio (RR) for included studies using a random effects model. For the institutional cohort portion of our study, we selected high cardiovascular-risk patients who received diagnoses of BC between 2010 and 2022 if they met our inclusion criteria. We performed a Cox proportional hazards model with stepwise adjustment.

Results

A pooled random effects model with 9 studies showed that patients with left-sided BC receiving EBRT had a 10% increased risk of CAD when compared with patients with right-sided BC receiving EBRT (RR, 1.10; 95% CI, 1.02-1.18; P = .01). However, subgroup analysis of 6 studies that included patients diagnosed after 1980 did not show a significant difference in CAD based on BC laterality (RR, 1.07; 95% CI, 0.95-1.20; P = .27). For the institutional cohort portion of the study, we found that patients with left-sided BC who received EBRT did not have a significantly higher risk of CAD when compared with their right-sided counterparts (hazard ratios [HR], 0.73; 95% CI, 0.34-1.54; P = .402).

Conclusions

Our study suggests a historical trend of increased CAD in BC patients receiving left-sided EBRT. Data from patients diagnosed after 2010 in our institutional cohort did not show a significant difference, emphasizing that modern EBRT regimens are safe, and laterality of BC does not affect CAD outcomes in the short term after a BC diagnosis.

Radiation Dose to Critical Cardiac Structures from Three-Dimensional Conformal Radiation Therapy (3D-CRT), Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) Techniques for Left-Sided Breast Cancer

A comparison of the radiation exposure to the left anterior descending artery (LAD) and left ventricle (LV) was performed for twenty-three left breast cancer patients. For each participant, two tangential fields 3D-CRT, two- and seven-field IMRT and two and four partial arcs VMAT plans were created. Dose constraints for CTV, ipsilateral lung and heart were followed. The V40Gy, V30Gy, Dav of LAD and V23Gy, V5Gy, Dav of LV were calculated and extracted from the plans. Parametric and non-parametric tests were applied to compare the parameters derived from the five treatment techniques. All generated plans fulfilled the dose constraints. The Dav ranges of the LAD and LV from all examined techniques were 11.77-14.73 Gy and 5.37-6.40 Gy, respectively. The V40Gy and V30Gy ranges of the LAD were 2.90-12.91% and 10.80-18.51%, respectively. The V23Gy and V5Gy of the LV were 4.29-7.43% and 18.24-30.05%, respectively. The VMAT plans and seven-field IMRT significantly reduced the V40Gy, V30Gy of LAD and V23Gy of LV compared with the two-field treatments (p < 0.05). However, 3D-CRT plans provided statistically lower values for V5Gy of LV over the other techniques (p < 0.05). The presented results provide a detailed dataset of the radiation burden of two critical cardiac structures from five radiotherapy techniques.