DOSIMETRIC COMPARISON OF 3 DIFFERENT TREATMENT TECHNIQUES IN PANCREATIC CANCER RADIOTHERAPY: RETROSPECTIVE STUDY

In our study, our aim is to treat 20 patients with pancreatic cancer who had radiotherapy, with conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT), volume modulated arc therapy (VMAT) planning and comparison of the techniques in terms of dosimetric. In this study, 20 patients with primary pancreatic head tumor who were treated in our clinic between 2012-2017 were retrospectively evaluated. Five different treatment techniques were planned for each patient’s tumor, around of tumor and regional lymph nodes, and all plans were implemented so that target volume doses would be 54/45 Gy. Plans were prepared using 6 MV X-rays for VMAT and IMRT and 15 MV X-rays for 3BKRT. Techniques were compared in terms of planned target volume doses (PTV), conformity index (CI), homogeneity index (HI), organs at risk (kidneys, spinal cord, liver). The mean CI indices VMAT 1 arc plans for PTV54 and PTV45 were found to be 1.16 and 1.03 for VMAT 2 arc 1.01 and 1.00. Although there was no significant difference between the two groups in terms of CI, the most appropriate CI value was found in VMAT 2 arc plans (p = 0.806 for PTV45 and p = 0.595 for PTV54). There was no difference in terms of CI between IMRT and 3D-CRT techniques, the best value being obtained from IMRT technique. Doses of VMAT 2 arc plans were found to be lower, although there was no statistical difference between VMAT 1 arc and VMAT 2 arc plans in terms of critical organ doses. Since pancreatic tumors are located close to critical organs such as kidneys and liver as a settlement, 3DCRT plans can be accepted in terms of liver; but the kidneys have not succeeded in terms of protection. The VMAT 2 arc technique excelled in dose sprinning, CI, HI and critical organ doses according to other techniques. Therefore, VMAT may be preferred as a treatment technique when side effects are taken into account