Main Session
Sep
29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3531 - Cardiac Substructure Dose and Cardiac Toxicity after SBRT for Central and Ultra-Central Lung Tumors: A Multicenter Retrospective Cohort Study
Presenter(s)
Axel Licha, MD - Institute Jean Godinot, Reims 51056, Grand Est
A. Licha1, A. Moignier2, Z. Hmad3, J. Bellec4, L. Duverge4, F. Felici5, L. Vaugier6, and A. Beddok7; 1Institute Jean Godinot, Reims, France, 2Institut de Cancérologie de l'Ouest René Gauducheau, Nantes, France, 3Institut Jean Godinot, Reims, France, 4Centre Eugene Marquis, Rennes, Bretagne, France, 5Centre de Haute-Energie, Clinique Maymard, Bastia, France, 6Institut de Cancérologie de l'Ouest René Gauducheau, France, Saint Herblain, France, 7Department of Radiation Oncology, Institut Godinot, Reims, France
Purpose/Objective(s):
Cardiac toxicity remains a clinically relevant concern after stereotactic body radiotherapy (SBRT) for central and ultra-central lung tumors. Although cardiac exposure is commonly evaluated using whole-heart dose metrics, the contribution of individual cardiac substructures to subsequent cardiac toxicity remains insufficiently characterized. This study aimed to comprehensively evaluate substructure-specific D0.1cc dose metrics and to determine whether these parameters are associated with clinically documented cardiac toxicity.Materials/Methods:
This retrospective multicenter dosimetric analysis was conducted within a previously reported cohort of patients treated with SBRT for central or ultra-central lung tumors between 2016 and 2023. Among 194 treated patients, 168 with available dosimetric data and follow-up were included. Cardiac toxicity was defined as CTCAE v5.0 grade =2 cardiac or great-vessel events occurring after treatment. D0.1cc dose metrics were extracted for 21 predefined cardiac substructures. Associations between substructure D0.1cc dose and time to cardiac toxicity were evaluated using univariable Cox proportional hazards models. Dose was analyzed as a continuous variable to preserve statistical power. Discriminatory performance was quantified using Harrell’s concordance index, with internal validation performed by bootstrap resampling (1,000 iterations). Exploratory cutpoint analysis was performed using maximally selected rank statistics to evaluate potential threshold effects.Results:
Seventeen cardiac toxicity events were observed during follow-up. Among 21 D0.1cc substructure parameters, proximal LAD D0.1cc was the only metric significantly associated with cardiac toxicity (HR per Gy 1.05, 95% CI 1.01–1.10, p=0.028). No whole-heart or alternative substructure D0.1cc metric demonstrated a significant association. A 5 Gy increase in proximal LAD D0.1cc corresponded to an estimated 28% relative increase in cardiac toxicity risk. Proximal LAD D0.1cc demonstrated modest discriminatory performance (bootstrap median c-index 0.59, 95% CI 0.44–0.74). Exploratory cutpoint analysis identified a separation around 5–6 Gy; however, dichotomized analyses did not demonstrate robust statistical separation, consistent with a progressive dose–response relationship rather than a distinct threshold.Conclusion:
Proximal LAD D0.1cc appears to be a relevant substructure-specific predictor of cardiac toxicity after lung SBRT and may provide more granular risk stratification than whole-heart metrics. These findings support anatomically guided cardiac dose optimization strategies and warrant validation in larger prospective cohorts.