EFFECT OF COMPLETE BLOCK OF IRRADIATED LUNG VOLUME IN BREAST CANCER WITH HELİCAL THOMOTHERAPY

Abstract: The purpose of this study was to evaluate the dosimetrics value of the  Tomo Helical (TH) plans with complete block where located posterior of the sided lung compared to TH plans with no block in patients with intact breast cancer. TH plans with intact breast cancer were retrospectively created for 17 patients with blocked or no TH techniques in our clinic. The beam angles were arranged to cover PTV intact breast and to minimize doses to Organ at Risks (OARs), sided lung and contralateral breast in TH plans. There was no difference between the values of Conformity Index (CI) and Homogenity Index (HI) of both plans (p>0.05). The values of Dmean, V5 and V20 of the sided lung in Tomo Helical with block (HTb) were significantly lower than that Tomo Helical with no block (TH) for all 17 patients (p=0.01, p=0, p=0.002). The values of Dmean and V5 of heart in HTb were significantly lower than that in TH (p=0.004, p=0). Both of HTb and TH plans produce acceptable target dose covarage in intact breast Radio Therapy (RT). Especially we produce lower dose V5 values in sided lung volume when, using complete block posteriorly. Aimed to decrease scattering low dose regions in irradiated volume and around the breast, so we may prevent probability of secondary malignancy in breast region.