Purpose: To evaluate the incidence and risk factors of enlargement of cardiac silhouette on chest radiographs after radiotherapy for esophageal cancer.
Materials and methods: We analyzed 67 patients with esophageal cancer who received external beam radiation therapy with a total dose of >or=50 Gy and were followed for >or=6 months. Sixteen patients received radiation alone, and the remaining 51 received chemoradiotherapy. The difference between the cardiothoracic ratio (CTR) on the pretreatment chest radiograph and that on the posttreatment radiograph with maximum cardiac silhouette for each patient was used for the analysis.
Results: The average maximum increase in CTR for the entire group was 4.5%, which was statistically significant. Only the area of the cardiac silhouette in the initial radiation field was a significant risk factor for enlargement of the cardiac silhouette. Pericardial effusions were observed in all patients who underwent computed tomography with severe enlargement of the cardiac silhouette.
Conclusion: The CTR value significantly increased after radiotherapy for esophageal cancer. Radiation-induced pericardial effusion may be the main cause of enlargement of the cardiac silhouette. The irradiated cardiac area was the only significant risk factor for enlargement of the cardiac silhouette; the use of chemotherapy was not.