A Comparison of VMAT, IMRT, and 3DCRT in the Treatment Planning of Patients with Distal Esophageal Cancer: 2234

Background: There is limited data comparing intensity modulated radiation therapy (IMRT) and 3D conformal radiation therapy (3DCRT) in node-negative patients with cancer of the distal esophagus. Methods: Eight patients with node-negative cancer of the distal esophagus measuring 1-5 cm tumors were selected for this study. Target volumes were generated for all patients based on standard current practice; 3DCRT and IMRT plans optimized to obtain minimum dose to the heart were then created using the using the Eclipse Treatment Planning. Conformality index (CI, the amount of target volume covered by the prescription dose) and conformation number (CN, the amount of normal tissue receiving prescription dose) were calculated. Dose volume histograms also were generated and clinically relevant parameters were extracted and compared for each planning modality using paired T-tests. Each patient served as his or her own control. Results: The difference in CI ranged from 0-0.01, indicating equivalent target coverage for each patient. IMRT produced superior CN (mean CN = 0.74) vs. the 3DCRT plans (mean CN = 0.45). Heart V40 and the maximum dose to spinal cord were lower for IMRT (mean difference in heart V40 = 34.5%, p=0.0006 and mean difference in the maximum dose to the spinal cord = 18.1 Gy, p=0.0005) but lung V5 and V20 were lower for 3DCRT (mean difference in lung V5 = -21.3%, p=0.0026 and mean difference in lung V20 = -5.2%, p=0.0014). Conclusions: When optimized to minimize dose to the heart, IMRT plans were substantially more conformal to the target structures with less dose to the heart as compared to 3DCRT plans; however this occurred at the expense of increased dose delivered to the lung.