Investigation dose distribution of intensity modulated radiotherapy on diagnosed head and neck cancer

According to localization and sexuality head and neck cancer occurance ratio is 6% of all cancer types. Intensity modulated radiotherapy provides tumor cells taking most effective dose whereas decreases dose of normal tissues. Purpose of our study is to compare analyzing dose distributions of diagnosed head and neck cancer treated by intensity modulated radiotherapy (IMRT) with international dose tolerance recommendation. Retrospective investigation of 30 head and neck cancer diagnosed patients who were treated by intensity modulated radiotherapy in Çukurova University Medical Faculty Radiation Oncology Department between the years 2009 and 2012 was done in our study. Age mean of patients were 60 (20-80) and male-females rate was 9/1. IMRT treatment plans of patients were created in the form of 1.8-2.0 Gy/Fr per week (28 patients with 9, 1 patient with 7 and 1 patient 6 treatment fields). In our study mean doses, homogeneity index and conformity index values of IMRT PTV70, IMRT PTV60 and IMRT PTV46 target volumes were investigated according to the ICRU 62 and ICRU 83 reports. Dose distributions of organs at risk were analyzed. In our study all doses be given which were 70 Gy and 60 Gy were delivered uniformly to IMRT PTV70 and IMRT PTV60 target volumes of patients with 100% ± 5%. 46 Gy dose was delivered to IMRT PTV46 target volumes with the average rate of 102.8%. Doses of parotid gland within the target volume of 15 patients and doses of oral cavity within the target volume of 13 patients exceeded the level of recommended tolerance dose. The highest value of maximum spinal cord doses remained under 50 Gy. Maximum eyes and maximum lens doses did not exceed the limit of maximum dose exception of one patient eyes dose. Maximum brain doses of 4 patients exceeded limit of 60 Gy dose. Doses of other organs at risk remained under the tolerance level. In accordance with the aim of IMRT method which is to minimize dose to the out of field tissues, it gives completely defined dose to target volume. On head and neck cancer treated by IMRT technique, homogeneity index values of target volume were determined to be closer to 1,0 (suitable value according to ICRU 62) and 0,0 (suitable value according to ICRU 83) value at high doses. Mean conformity index values of target volume were determined according to the ICRU 62 as 0.98 and according to the ICRU 83 as 0.95. The primary aim on radiotherapy is to increase treatment effectiveness. While patient is being treated to provide tumour control, it necessities to exceed the dose limits of organs at risk. Key Words: Radiotherapy, Head and neck cancer, Target volume, IMRT PTV70, Homogeneity index.