Lung Cancer

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TU_23_3542 - Dosimetric Predictors of Cardiotoxicity in Thoracic Radiation Therapy for Lung Cancer

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Dosimetric Predictors of Cardiotoxicity in Thoracic Radiation Therapy for Lung Cancer
J. Borkenhagen1, S. Klawikowski1, L. Rein2, and E. M. Gore3; 1Medical College of Wisconsin, Milwaukee, WI, 2Medical College of Wisconsin Department of Biostatistics, Milwaukee, WI, 3Medical College of Wisconsin and Clement J Zablocki VA Medical Center, Milwaukee, WI

Purpose/Objective(s): Higher cardiac dose when treating locally advanced lung cancer is associated with worse overall survival (OS), although the direct association between cardiac dose and early cardiotoxicity is poorly understood. We assessed the impact of dose to the heart and substructures in patients treated at our institution with curative intent radiation therapy (RT) for lung cancer. We hypothesized that cardiac dose is associated with early cardiotoxicity and worse OS.

Materials/Methods: We identified 76 patients treated with thoracic RT for lung cancer receiving a dose of >= 44 Gy at 1.5-3 Gy per fraction at our institution from 2010-2015 and retrospectively reviewed their charts. Progress notes, imaging, EKGs, and echocardiograms were reviewed to identify cardiac events occurring after the start of RT. Baseline characteristics for cardiac risk including age, preexisting cardiac disease, smoking, and diabetes were also collected. Cardiac sub-structures including atria, ventricles, pericardium, and coronary space (base of heart) were contoured for each case, and dose-volume (DV) parameters of interest were extracted. Univariate Cox proportional hazards analysis was used to identify DV predictors of cardiotoxicity and OS. Wilcoxon rank-sum analysis was used to assess the relationship of tumor location to DV parameters.

Results: Seventy-six cases were evaluated with a median follow-up of 1.2 years. Cardiac toxicities observed included atrial arrhythmia (n = 5), trace pericardial effusion (n = 3), small to moderate pericardial effusion (n = 13), and valve disease (n = 1). Significant pericardium (structure encompassing all cardiac substructures) DV predictors for cardiotoxicity included Dmean (HR 1.05, p = 0.015), V30 (HR 1.03, p = 0.010), and V45 (HR 1.05, p = 0.004). Atria and ventricle Dmean, V30, and V45 were each significant predictors of cardiotoxicity. Dmax to pericardium, atria, and ventricles however were not significant cardiotoxicity predictors, nor were total heart volume or PTV volume. No cardiac DV parameter was a significant predictor for the outcome of OS. However, cardiotoxicity itself was a time-dependent predictor of worse OS (HR 3.28, CI [1.52, 7.07], p = 0.002). Tumor location in the left lower lobe was also a predictor of worse OS (HR 2.80, CI [1.167, 6.720], p = 0.021). Patients with left lower lobe tumors had a higher ventricular V30 (p = 0.09) relative to patients with tumors in all other locations.

Conclusion: Early cardiac events were relatively common after curative intent RT for lung cancer and associated with multiple cardiac DV parameters. Additionally, the occurrence of early cardiotoxicity was associated with worse OS. Multivariable analysis to further evaluate the relationship among cardiac dose, early cardiotoxicity, and OS will be performed and presented.

Author Disclosure: J. Borkenhagen: None. S. Klawikowski: Employee; Green Bay Oncology. L. Rein: None. E.M. Gore: Partner; Stuart Wong. Advisory Board; NRG Oncology. Co-Chair Publications Committee; NRG Oncology.

Jenna Borkenhagen, MD

Medical College of Wisconsin

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