Moving From 2d To 3d Conformal Radiotherapy (3dcrt) In Locally Advanced Head And Neck Cancer: A Dosimetric Comparison

16530 Background: The aim of this study is to evaluate the dosimetric parameters of 3D CRT in head and neck tumors, to compare with hypothetical 2D plans, and to evaluate the acute toxicity. Methods: A total of 33 patients with median age of 62 years (range: 23–87 ) and with histologically proven head and neck cancer were consecutively treated with 3D CRT using a 6-field photon beam technique. 9 patients had supraglottic carcinoma, 5 - glottic carcinoma, 4- nasopharyngeal carcinoma, 4 - thyroid carcinoma, 2- oropharyngeal cancer, 3 - carcinoma of oral cavity, 1- carcinoma of hypopharynx, 1- maxillary sinus carcinoma, 3- unknown primary, 1- recurrent laryngeal carcinoma. 28 patients received concomitant chemotherapy and 13 were treated with neoadjuvant chemotherapy, 5 patients received postoperative radiotherapy and 28 received definitive radiotherapy. A comparative analysis of dose distributions and dose-volume histograms (DVH) between 2D and 3D plans for 11 patients with glottic and supraglottic carcinoma for the initial 50 Gy (since the 20 Gy boost was given almost identical in both technique) was carried out. Toxicity analysis was determined according to RTOG/EORTC toxicity criteria. Results: The mean dose coverage V45 (%) of the primary planning target volume for 2D and 3D plans was 89.6% and 94.8%, respectively (p=0.005). The mean volumes of the hot spots ( 110% of prescribed dose) for primary target volumes for 2D and 3D plans were: 61cc (range: 8.7–130.2 cc) and 26.2 cc (range: 0–49.8 cc), respectively (p=0.005). The mean dose to the parotid glands was significantly lower with 3D CRT (22.1 Gy and 24.7 Gy) compared to 2D technique (45.2 Gy and 46.4 Gy) for right and left parotids, respectively (p=0.003). The maximal spinal cord dose was: mean 45.3 Gy and 41.6 Gy for 2D and 3D CRT, respectively (p=0.003). Gr3 acute toxicity was observed in 3 patients (9%) , and Gr 4 toxicity in 6 patients ( 18%). Treatment was interrupted in 3 patients only. Conclusions: 3DCRT in head and neck cancer permits good coverage of the PTV .The low rate of acute toxicity can be explained by improving the dosimetric parameters of organs of risk and reducing the volume of hot spots in the target. Using 3D CRT for laryngeal carcinoma allows parotid sparing with a mean parotic dose of less than 26 Gy No significant financial relationships to disclose.