Changes in Cardiac Volume during Concurrent Chemoradiotherapy for Esophageal Cancer Based on Repeated Enhanced 4DCT

Abstract

Concurrent chemoradiotherapy is considered curative intent treatment for patients with non-operative esophageal cancer. Radiation-induced heart damage receives much attention. The aim of this study was to detect the change of cardiac volume over the course of radiotherapy for esophageal cancer based on repeated enhanced 4DCT and to explore the factors that might affect the change in cardiac volume during radiotherapy. In this prospective study, forty-six patients with pathologically proven thoracic esophageal squamous cell carcinoma who were scheduled to receive concurrent chemoradiotherapy with a total dose of 60Gy in 30 fractions in our department were enrolled in the study. All the patients underwent enhanced 4DCT and 3DCT scans before radiotherapy and then repeated the CT scans every 10 fractions during treatment. The heart was contoured on 3DCT, end expiratory (EE) of 4DCT and maximum intensity projection (MIP) of 4DCT by the same radiation oncologist according to the same guidelines. Heart volumes and other relative parameters during radiotherapy were analyzed. Compared with the initial value, heart volume decreased significantly at the tenth fraction (reduction = 3.27%, 4.45% and 4.52%, respectively, on 3DCT, EE and MIP, p < 0.05) and the twentieth fraction (reduction = 6.05%, 5.64% and 4.51%, respectively, on 3DCT, EE and MIP, p < 0.05). The reduction between the initial measurement and the measurement at the thirtieth fraction was not significant (p > 0.05). There was a decrease in both systolic (16.95 ± 16.69 mmHg, p < 0.05) and diastolic blood pressure (7.14 ± 11.64 mmHg, p < 0.05) and an increase in heart rate with 5.27 ± 6.25 beats/min (p < 0.05) after radiotherapy. The patients with mid-thoracic esophageal cancer were found to have significantly greater heart dose than the upper and lower tumors (p <0.05). None of the potential explanatory variables correlated with heart volume changes. By eliminating the effect of respiratory motion on the heart, 4DCT better reflects changes in cardiac volume during radiotherapy of esophageal cancer. Heart volume was significantly reduced in the early treatment stage and maintained the reduction until the middle treatment stage, then showed a tendency to restore to the initial level at the thirtieth fraction. The blood pressure decreased and the heart rate increased during radiotherapy. These observed changes may be valuable indicators of cardiac impairment and target dose changes.