DVH comparison of three-dimensional conformal and conventional radiotherapies in normal tissues of patients with nasopharyngeal carcinoma

AIM: To investigate the effect of three-dimensional conformal radiotherapies (3D-CRT) and conventional radiotherapies on normal tissues in patients with nasopharyngeal carcinoma by comparing the dose distribution in normal tissues so as to pick out the better method. METHODS: Forty cases of nasopharyngeal carcinoma (18 cases at stage T1 and 22 at stage T2, according to 92 Fuzhou staging) underwent conventional radiotherapy and 3D-CRT respectively. Treatment planning system (TPS) was used to mark the dose distribution and quantity in normal tissues (bilateral lens, optic nerves, brain stem, spinal cord, parotid glands and temporomandibular joints) and the data obtained were analyzed with dose-volume histogram (DVH). The major fields in conventional radiotherapy were bilateral neck-conjoined horizontal field and pre-auricular field, the pre-nasal. The top-head fields were respectively added in the first and second phases in 3D-CRT and 3 to 5 conplane or non-conplane fields were designed in the third phase. The prescribed dose of the two groups was 70Gy respectively. RESULTS: 3D-CRT had satisfactory dose coverage of target volume of nasopharyngeal carcinoma compared with conventional radiotherapy. 3D-CRT plans spared more parotid glands and two-side lens than conventional treatment (P0.05), the conventional treatment spared a little more brain stem and bilateral optic nerves than 3D-CRT(P0.05) and the received dose in other organs was similar in the two plans(P0.05). CONCLUSION: 3D-CRT not only satisfies the dose coverage of target volume, especially in subclinical lesion region, but also spares more normal tissues compared with conventional radiotherapy.