137MO - Impact of cardiac substructure dose on cardiotoxicity and overall survival (OS) in early-stage non-small cell lung cancer (ES-NSCLC) patients receiving stereotactic ablative body radiotherapy (SABR): Data from the interim analysis of the LUNG HEART study

Background

The rationale of the interim analysis of the LUNG HEART prospective study is to investigate for any existing association between the dose delivered to heart substructures and the development of cardiotoxicity and OS in ES-NSCLC patients treated with SABR.

Methods

14 cardiac substructures and 7 great vessels of the heart were manually contoured with dual verification to collect dosimetric data. Follow-up was calculated from the start of RT using the reverse Kaplan-Meier method. Cardiac events (CEs) were evaluated according to CTCAE 5.0 classification. The Fine and Gray competing risk regression model was used to predict the cumulative incidence of grade 3 or higher (G≥3) CEs, considering non-cardiac death as a competing risk. Cox regression model was used to assess associations between covariates and OS. Local control (LC), progression free survival (PFS) and OS was estimated with the Kaplan-Meier method.

Results

From March 2019 to December 2023, 142 patients were enrolled with a median age of 78 years. With a median follow up of 35 months, 2 year-LC was 89%. The median PFS was 36 months (2 year-PFS 67%) and the median OS was 43 months (2 year-OS 69%). Death was documented in 61 (43%) patients, in 31 (51%) for non-neoplastic causes. 76 (53%) patients had a pre-existing cardiac disease. 21 (15%) patients developed a first G≥3 CE at a median of 10 months. Patients with pre-existing heart conditions had a higher 2-year cumulative incidence of the first G≥3 CE (16% vs 8.2%; p=0.037). The Fine and Gray multivariable analysis showed a statistically significant association between pre-existing cardiac diseases (hazard ratio [HR]: 2.72; p=0.03), left anterior descending coronary artery (LAD) mean dose (HR: 1.20; p=0.002) and G≥3 CEs. Furthermore, a higher dose to the coronary trunk at 0.5cc was linked to worse OS (HR: 1.21; p=0.06) in the Cox multivariable analysis.

Conclusions

In ES-NSCLC patients treated with SABR, pre-existing cardiac diseases and higher mean doses to the LAD significantly increased the risk of developing G ≥ 3 CEs. Additionally, a higher dose to the coronary trunk was associated with poorer OS.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.