Comparing Different Treatment Plans in Radiotherapy of Hodgkin Disease Involving Neck and Mediastinum, Using Parallel-Opposite Fields Method

Hodgkin lymphoma is one of the treatable malignant diseases. The incidence of secondary cancers, especially breast cancer, and cardiovascular diseases after radiotherapy doubles the importance of patient treatment plan. In this study, some comparisons were made between a variety of treatments by using photon energy of 6 and 18 Mv on the treated areas of neck and mediastinum.
The contouring of all sensitive organs and treatment volumes were performed for 18 female patients with Hodgkin lymphoma involving neck and mediastinum, using TiGRT software. Then, comparison between different anterior-posterior (AP-PA) treatments with different weights of 6 and 18 Mv was done.
Findings: Using 18-Mv photon with the same weight of the anterior and posterior than conventional 6-Mv photon caused 2-9% reduction in mean dose to breast, heart, and lungs. Although changing the normalization (isocenter) point from the center of tumor to sternal notch reduced the mean dose of the studied organs, 9-13% reduction in the mean dose of treatment volume did not meet the criterion (prescribed dose ± 105%).
For women with Hodgkin lymphoma involving mediastinum and neck, using 18-Mv photon with the same weight of the anterior and posterior is more appropriate to meet the design criteria of treatment (coating suitable treatment volume of prescribed dose ± 105%). Changing isocenter point from the center of the tumor to sternal notch causes a more favorable result. The better uniformity of the dose distribution in treatment volume is achieved by using 18-Mv photon.