Dosimetric evaluation of different treatment planning techniques in patients with mediastinal hodgkin lymphoma

The purpose of this study is the comparison of 3DCRT and VMAT planning techniques used in the treatment of Mediastinal Hodgkin Lymphoma in terms of their capability of covering around target structures and critical doses as well as the application of these treatments techniques. Lymphomas are the cancer at white blood cells which is called lymphocytes. Lymphomas are divided into two groups: Hodgkin Lymphoma (HL) and Non- Hodgkin Lymphoma (NHL). The treatment options for the patients with Lymphoma are chemotherapy, radiotherapy, immunotherapy, high dose chemotherapy and transfer of stem cells depending on the type and the level of lymphoma, and other factors. The main treatments of Hodgkin Lymphoma are chemotherapy and radiotherapy. In some condition, both of treatments are used together or one of them is used. The radiotherapy plays an important role for Mediastinal Hodgkin Lymphoma which is the cancer type of lymphoma. With the help of the developing technology, the technique of Arranging Intensity Radiotherapy, new technologic treatment, is used often as well as the technique of 3DCRT. In our study, the treatment planning was created by techniques of 3DCRT and VMAT at 10 patients with Mediastinal Hodgkin Lymphoma. In 3DCRT, 6-15MV photon energy is used to irradiate back and front of patients. The plans of VMAT consist of 3 parsiel arc with 6MV photon energy, and of irradiation except arms. In the both of planning techniques, the treatment doses are the same; 1.8 Gy per day fraction, totally 30.6 Gy. When we comprise VMAT and 3DCRT techniques, VMAT has more advantages than 3DCRT according to the homogeneity index and the conformity index. When we examine the doses of critical organs, 3DCRT technique has more statistically advantages than VMAT in terms of the values of lung; V5 (p=0,005), V10 (p=0,007), V15 (p=0,047), Dmean (p=0,037) and the values of right breast; V5 (p=0,012), V10 (p=0,018), Dmean (p=0,018). VMAT has more statistically advantages than 3DCRT according to the values of lung; V20 (0,009), V25 (p=0,005) ve V30 (p=0,005), the values of heart; V10 (p=0,028), V15 (p=0,005), V20 (p=0,005), V25 (p=0,005), V30 (p=0,011) and Dmean (p=0,008), the values of spinal cord; V20 (p=0,013), V25 (p=0,005), V30 (p=0,005), Dmean (p=0,007) and Dmax (p=0,005), the values of left breast; V20 (p=0,018), V25 (p=0,018) and V30 (p=0,027), and the values of esophagus; Dmean (p=0,013). Both of techniques give same values V5 (p=0,333 ve p=0,093) of heart and spinal cord, V15 (p=0,08), V20 (p=0,066), V25 (p=0,068), V30 (p=0,068) of right breast and V5 (p=0,123), V10 (p=1), V15 (p=0,397) ve Dmean (p=0,735) of left breast. 3DCRT technique is more advantageous than VMAT in terms of low doses like the doses of outside PTV organs. However, at high doses VMAT is better than 3DCRT. In consequence of our study, VMAT is better than other technique in terms of the covering around the target structures additionally, the dose limit of the critical organs. Key words: Lymphoma; Radiotherapy; 3DCRT; VMAT