Radiation dose to heart and cardiac substructures associated with cardiac events and survival in lung cancerRadiation dose levels linked to heart health in lung cancer patients

This meta-analysis evaluated the impact of radiation dose to the whole heart (WH) and specific cardiac substructures (CS) on clinical outcomes in a large cohort of 21,645 patients with lung cancer who had undergone radiation therapy. The study aimed to identify specific dosimetric thresholds and parameters that correlate with cardiac complications and overall survival.

The primary outcomes analyzed were cardiac events (CEs) and patient survival. The analysis focused on various radiation metrics, including Mean heart dose (MHD), ventricle dose, and LAD dose, as well as specific substructure parameters such as LAD V15, LPV V55, RPV V10, RA V60, and LMA V10. These metrics were evaluated to determine their predictive value for different types of cardiac complications.

Regarding major adverse cardiac events (MACE), the study found that LAD V15 was significantly associated with MACE. Furthermore, a specific threshold of LAD V15 <10% was identified as having potential predictive value for MACE. For ischemic events, the analysis reported that Mean heart dose (MHD), ventricle dose, and LAD dose were significantly associated with these events. Survival was also linked to radiation metrics, with MHD significantly associated with survival; additionally, CS parameters, particularly the heart base dose, showed predictive value for survival.

Specific arrhythmia subtypes were associated with various cardiac substructure parameters. For atrial fibrillation (AF), the study identified specific thresholds: LPV V55 <2% and RPV V10 <54% were noted as having potential predictive value. For non-AF supraventricular tachyarrhythmia, RA V60 <0.03 cc was identified as a potential predictive threshold. Bradyarrhythmia was associated with a threshold of LMA V10 ≥1 cc.

Pericardial effusion was also linked to specific radiation doses. The study found that MHD, heart V5/V35/V55, and pericardial doses were significantly associated with the occurrence of pericardial effusion. These findings suggest that specific regions of the heart and pericardium are particularly susceptible to radiation-induced damage.

While the study provides a large sample size of 21,645 patients, it is important to note that the results are based on associations between dosimetric parameters and clinical outcomes. No specific safety data regarding adverse events, serious adverse events, or treatment discontinuations were reported in the study. The results provide a framework for understanding radiation-induced heart injury mechanisms and may inform future protective strategies.

Methodological limitations were not reported. However, the clinical implications are significant for radiation oncology, as these findings may help in refining radiation planning to mitigate cardiac risks. Questions remain regarding the clinical utility of the specific thresholds identified, such as LAD V15 <10% or LPV V55 <2%, and how these can be integrated into routine clinical practice to improve outcomes for lung cancer patients.