Impact of lung and heart dose on survival after radiotherapy for esophageal cancer.

Abstract

3 Background: Chemoradiation is an essential tool in treatment of localized esophageal cancer. Recent data indicates that cardiac dose is an independent predictor of survival after chemoradiation for locally advanced lung cancer. However, the impact of normal tissue dose in esophageal cancer has not been well characterized. We investigated cardiac and pulmonary dose-volume histogram (DVH) metrics as potential predictors of overall survival (OS) after chemoradiation for esophageal cancer. Methods: We reviewed 453 consecutive patients with stage I-III esophageal cancer treated with definitive or preoperative chemoradiation (median dose 50.4 Gy in 28 fractions) between 2007 and 2015 at our center. Most (n = 442) received intensity-modulated radiation therapy. Radiation plans were reviewed and multiple DVH metrics for heart (max and mean dose, V5Gy, V10Gy, V20Gy, V30Gy, and V40Gy) and lung (mean dose, V5Gy, and V20Gy) were extracted for analysis. Other clinical covariates (surgery, performance status, stage, and histology) were recorded. Cox univariate (UVA) and multivariate (MVA) regression was used to analyze the association of these factors with overall survival. Results: Median follow-up for surviving patients was 28.4 months. On UVA, older age, lower performance status, Stage III disease, lack of surgery, heart V40Gy, lung V5Gy, lung V20Gy, and lung mean dose were significantly associated with decreased survival. On MVA, surgery (p = 0.008), stage III disease (p < 0.0002) and lung V20Gy (p = 0.0389) remained significant, while heart V40Gy did not (p = 0.211). Patients with lung V20Gy< 20% had a median survival of 44.0 months, compared to 24.0 months for patients with lung V20Gy≥20%. Conclusions: This comprehensive dosimetric analysis of heart and lung dose in a large cohort of esophageal cancer patients suggests that lung dose is a significant independent predictor of survival. Cardiac dose was not independently predictive after adjusting for lung dose and other clinical factors. This data suggests that esophageal cancer outcomes may be improved by minimizing lung dose, particularly the volume receiving 20Gy or more, and provides further rationale for pursuing new techniques to reduce lung dose, such as proton therapy.