Abstract
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.
Highlights
Radiotherapy is the primary treatment modality for the inoperable or unresectable esophageal carcinoma
The drawback of non-coplanar intensity-modulated radiation therapy (IMRT) is that, even within toxicity tolerance, it could deliver a higher dose to the heart and spinal cord compared to the coplanar plan
For patients with cardiology and neurology concern, non-coplanar IMRT should be used with caution
Summary
Radiotherapy is the primary treatment modality for the inoperable or unresectable esophageal carcinoma. The goal of radiotherapy for esophageal cancer is to kill the cancer cell inside the target volume while sparing the normal tissues. Intensity-modulated radiation therapy (IMRT) has been broadly used in treating esophageal carcinoma [1]. IMRT has been proven to be superior to Three Dimensional Conformal Radiotherapy (3DCRT) with respect to dose conformity in Planning Treatment Volume (PTV) and the normal tissue preservation [2,3]. Depending on the volume and location of the esophageal cancer tumor, the normal lung tissue may be exposed to high doses of radiation. Several studies have shown that the incidence and severity of radiation pneumonia were related to the irradiation to normal lung tissue in esophageal carcinoma radiotherapy. From a clinical aspect, decreasing the side effect of radiotherapy is another way to improve the survival rate
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