Heart V5 predicts cardiac events in unresectable lung cancer patients undergoing chemoradiation.

Background: Recent studies incorporating dose escalated radiation identified heart dose as a predictor of cardiac toxicity in unresectable lung cancer patients. Whether conventionally dosed radiation impacts cardiac events remains unclear.

Methods: Stage III lung cancer patients undergoing definitive chemoradiation to 60-70 Gy were analyzed. Clinical and dosimetric factors (mean heart dose, heart V5-60 in 5 Gy increments) were analyzed against freedom from ≥ grade 3 cardiac events and overall survival (OS) by log-rank test. Multivariable analysis (MVA) for factors significant on univariate analysis was performed by Cox proportional hazards.

Results: A total of 108 patients were identified. Median follow-up was 18.0 months. One- and two-year OS were 79% and 61%, respectively. On MVA, gross tumor volume (GTV) ≥98.6 cm [hazard ratio (HR): 2.11, 95% confidence interval (CI): 1.15-3.93, P=0.02] and female gender (HR: 2.01, 95% CI: 1.09-3.73, P=0.03) predicted for worse survival. Twelve patients (11%) developed ≥ grade 3 cardiac events. One- and two-year freedom from cardiac events (FFCE) was 94% and 84% respectively. On MVA, heart V5 ≥49% predicted for cardiac events (HR: 11.44, 95% CI: 1.31-111.60, P=0.03) while female gender was nearly significant (HR: 3.49, 95% CI: 0.97-16.80, P=0.06). Females presented with similar comorbidity scores, GTVs, and relapse rates but experienced higher heart doses than their male counterparts.

Conclusions: Heart V5 ≥49% predicted for cardiac events after chemoradiation. However, cardiac dosimetry was not associated with survival. Rather, female gender and GTV ≥98.6 cm led to worse survival. This study corroborates emerging data that low-dose radiation to the heart impacts cardiac toxicity.