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Session: Therapy: Outcome Modeling and Assessment I [Return to Session]

Impact of Heart Irradiation On Survival (OS) in Two Patient Cohorts: Locally Advanced Non-Small Cell Lung Cancer (NSCLC) Patients (pts) Treated Conventionally and Early Lung Cancer Patients Treated with Lung SBRT

J Hu1, J Li2, S Schild3, J Anderson3, M Fatyga3*, (1) Arizona State University, ,,(2) Georgia Institute of Technology, ,,(3) Mayo Clinic Arizona, Phoenix

Presentations

MO-IePD-TRACK 6-3 (Monday, 7/26/2021) 12:30 PM - 1:00 PM [Eastern Time (GMT-4)]

Purpose: Recent evidence suggests that heart irradiation decreases OS in patients treated with radiation therapy (RT) for locally advanced (LA) NSCLC. Less is known about cardiac toxicity pts who receive SBRT to the lung.

Methods: 134 pts treated for LA-NSCLC with conventionally fractionated RT and 197 pts treated for early stage cancer with lung SBRT at Mayo Clinic Arizona were included in this study. Each group was analyzed separately. We used a multivariate Cox model Akaike Information Criterion (AIC) to select patient specific covariates predictive for OS. We digitally subdivided each heart into 64 segments and used a multivariate Cox model with patient specific covariates V%_D for each segment to determine irradiated segments predictive for OS. We used a clustering algorithm to determine irradiated heart regions predictive for OS.

Results: 134 patients were treated for LA-NSCLC (median dose: 62Gy, 1.8-2.0 Gy/fx) and 197 pts were treated with SBRT (48Gy in 4fx and 50Gy in 5fx). High doses delivered to the right-superior region of the heart were predictive for decreased OS in LA-NSCLC patients. The best predictive index was V%_55Gy (HR = 1.04/1%, p<0.01). Low doses to the inferior region of the heart were predictive for decreased OS in SBRT patients. The most predictive index was V%_2Gy (2Gy equivalent dose, HR = 1.01/1%, p=0.01). The LA-NSCLC model applied to SBRT patients did not predict a reduction of OS because of significantly lower doses to the heart in SBRT treatments.

Conclusion: Heart irradiation is associated with reduced OS in LA-NSCLC patients and in patients treated with lung SBRT. A comparison of the two patient cohorts suggests that different etiologies may be responsible for reduced OS in each.

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