Dosimetric Study of Coplanar and Non-Coplanar Intensity-Modulated Radiation Therapy Planning for Esophageal Carcinoma

摘要

Purpose: To compare the dosimetric impact of coplanar intensity modulated radiation therapy (IMRT) and non-coplanar IMRT for the esophageal carcinoma. Methods: There are forty-five esophageal carcinoma patients, fifteen of whom were cervical and upper thoracic (Group 1) and thirty were middle and lower thoracic (Group 2). Gross tumor volume (GTV), clinical target volume (CTV), and organs at risk (OAR) were contoured by the chief physician in the CMS-XiO treatment planning system. For each patient, one coplanar plan and two non-coplanar plans have been created using the same physical objective function. A detailed dose-volume histogram (DVH) comparison among three plans was then carried out in a tabulated format. Results: 1) In Group 1 patients with PTV volume less than 100cc, the mean dose and dose gradient of non-coplanar plan were much better than those in coplanar plan. 2) In Group 2 patients, the conformity index (CI) for coplanar and two non-coplanar plans were 0.69 ± 0.13, 0.41 ± 0.13, and 0.68 ± 0.15, respectively. The V5, V10, V20, and the mean dose to the lung were lower in the non-coplanar plans compared to ones in coplanar plan. However, the non-coplanar plans resulted in an increase in a dose to the heart, but the dose was still within heart toxicity tolerance. Conclusion: For Group 1 patients, the non-coplanar IMRT plan had less dose gradient and better mean dose than the coplanar IMRT plan. For Group 2 patients, the non-coplanar IMRT could the decrease dose to the lung tissue, thus lowering the probability of radiation pneumonia to esophageal cancer patients. The drawback of non-coplanar IMRT is that, even within toxicity tolerance, it could deliver a higher dose to the heart and spinal cord compared to the coplanar plan. Therefore, for patients with cardiology and neurology concern, non-coplanar IMRT should be used with caution.