| Objective:To compare dose distribution and treatment results by three different EBRT techniques, CRT,late-course 3DCRT and IMRT, in primary NPC.Methods and materials: The data of 198 hospitalized primary NPC patients treated in the Department of Radiotherapy of Cancer Hospital of Guangxi Medical University between September 2006 and September 2007 were retrospectively analyzed. Eight cases were selected from the 198 patients mentioned above and there are two patients for every clinic stage. The CRT, late-course 3DCRT and IMRT plans were designed for every one of the eight to compare the planning in dose of target volume, protection of OARs and the related volume among the plans and carried out by the TPS. The stage distribution of all the 198 (by the Fuzhou Staging Classification, 1992) was 7, 64, 81 and 46 patients in Stage I, II, III and IV. Three different EBRT techniques were used: 127 Patients with CRT, 39 Patients with late-course 3DCRT and 32 patients with IMRT. Among the total patients, there are 102 with radiotherapy alone and 96 with concurrent chemotherapy. Definitive radiotherapy was given to all patients and the total dose was 68～80Gy. With a median follow-up of 14 months (range 4-21), to compare the acute phase response and treatment result.Results: At CTV1 and CTV2, the average mean dose by IMRT, which was the closest to prescription dose than by CRT and late-course 3DCRT (P<0.05). The prescribed dose coverage for by IMRT was also superior to other two techniques (P<0.05). The average maximum dose of brain stem and spinal cord by IMRT were 57.25Gy and 42.52Gy. The average mean dose of parotid, temporal, TMJ and mandible by IMRT were 38.66,19.84,44.53,43.5Gy, and the volume covered by more than TD5/5 at the OARs mentioned above were less than by CRT and late-course 3DCRT (P<0.05). At lens, it was higher that the delivered dose by IMRT than by CRT and late-course 3DCRT techniques (P<0.001). The morbidity of acute xerostomia in group IMRT, late-course 3DCRT and CRT were 6.3%, 15.4% and 18.9% in level 2 (X2=11.014,P=0.004, CRT and late-course 3DCRT, IMRT P=0.000). The severity of acute mucosa was better in group radiotherapy alone than in group synchronous radiotherapy and chemotherapy(X2=4.054,P=0.044), 18.6% and 34.4% in level 4 and 35.3% and 26% in level 0. The morbidity of xerostomia in 1-year later was lower in group IMRT and late-course 3DCRT than in group CRT (X2=7.012,P=0.03, CRT and late-course 3DCRT, IMRT P=0.000), 12.5%, 23.7% and 35.2%, respectively. The 1-year overall survival of total 198 patients was 96.6%, and the grouP of CRT,late-course 3DCRT,IMRT were 94.7%,100%,100% , respectively(X2=3.884,P=0.143). According to the clinical staging , the survival rate was significantly lower in stage IV than in stage I, II and III, they were 86.7 % and 100%,100%,98.7%, respectively(X2=10.76,P=0.013).Conclusions: Firstly, more complete target dose coverage was given by IMRT. Secondly, lower dose and smaller volume covered by more than TD5/5 were obtained by IMRT for brain stem, spinal cord, temporal, pituitary, optic nerve, parotid, TMJ and mandible. Thirdly, higher dose in lens was given by IMRT. Fourthly, it is lower morbidity of xerostomia in the acute phase that by IMRT and late-course 3DCRT than by CRT. Fifthly, it is more serious toxicities in oral mucosal that by synchronous radiotherapy and chemotherapy than by radiotherapy alone.
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