Predictive factors for acute esophageal toxicity in thoracic radiotherapy

Acute esophageal toxicity (AET) is a common complication and dose-limiting toxicity in thoracic radiotherapy. Previous studies demonstrated several clinical and dosimetric parameters of AET in patients with lung cancer. However, there are few reports dealing with these variables in intra-thoracic malignancies, including lung cancer and other thoracic malignancy. The purpose of this study was to evaluate the clinical and dosimetric factors associated with AET in patients with intra-thoracic malignancies. We examined 61 patients with intra-thoracic malignancies treated with radiotherapy: 34 patients with non-small-cell lung cancer (55%), 9 cases with small-cell lung cancer (15%), 7 cases with thymic cancer (11%), 4 thymomas (7%), 2 malignant lymphomas (3%), one seminoma (2%), one liposarcoma (2%), and 3 cases of other malignancies (5%). Radiotherapy was performed with a median dose of 60 Gray (Gy) (range 40-67 Gy). AET was graded according to the Radiation Therapy Oncology Group (RTOG) criteria. The following parameters were analyzed with respect to associations with AET by univariate and multivariate analyses: age, gender, thoracic surgery before radiotherapy, concurrent chemotherapy, duration of radiotherapy, maximum esophageal dose, mean esophageal dose, and percentage of esophageal volume receiving from 10 Gy (V10) to 65 Gy (V65), in 5-Gy increments. 43 patients (70%) developed AET: 36 patients (59%) with AET of RTOG Grade 1, 7 patients (11%) with Grade 2, and no patients (0%) with Grade 3 or worse. On multivariate analysis, V35 > 30% was the most statistically significant factor associated with mild AET (p = 0.013). Our findings provide a better understanding of the factors related to AET, and might be useful in designing a treatment plan to prevent severe esophageal toxicity.