| Objective: To observe the treatment effectiveness of radiotherapy on untreated nasopharyngeal carcinoma. Analyze the patterns of treatment fail- ure. The different dose distribution of target volume and normal tissues nea- rby are studied by comparing conventional radiotherapy(CRT) plan with int- ensity-modulated radiotherapy(IMRT) plan.Methods: Between November 2004 and November 2008, 68 patients with nasopharyngeal carcinoma received radical radiotherapy. According to the 2008 staging system, the disease was Stageâ… in 1, Stageâ…¡in 33, Stageâ…¢in 23and Stageâ…£in 11. Radiotherapy was delivered by two different tec- hniques: conventional radiotherapy in 31 patients and IMRT in 37 patients. We used CT simulation to design the field and make the plan in convention- al radiotherapy, taken two lateral faciocervial photon fields and an anterior field. IMRT treatment plan was accomplished by the inverse treatment plan- ning system Eclipse. Different prescribed dose was delivered to Gross tum- or volume(GTV) and Clinical tumor volume(CTV). The GTV, CTV and upp- er neck were irradiated by IMRT technique. The lower neck and supraclavi- cular fossae were irradiated with the conventional technique using an anter- ior field. Two aspects were assessed by using Dose volume histogram: the uniformity and conformity of dose distribution in Tar- get Volume, and dose delivered to Organ at Risk (ORA). The Kaplan-Meier method was used to calculate the local regional control rate, distant metastases-free rate and ov- erall survival rate. Acute and late toxicities were graded according to RTOG radiation morbidity scoring criteria.Results: With a median followed-up of 17 months, 20 patients were tr- eatment failure. There had been 2 progression at the primary site, 6 local re- currence at the primary site, 1 patient failed in the neck. 11 patients develo- ped distant metastasis. 11 patients had died for two reasons: progression of primary tumor in 4 patients, distant metastasis in 7 patients The 1-, 2-, 3- year estimated local-regional control rates were 93.5%, 84.6% and 84.6% respectively. The 1-, 2-, 3-year distant metastasis-free rates were 92.4%, 74.5% and 70.4% respectively. The 1-, 2-, 3-year overall survival rates were 93.7%, 76.6% and 76.6% respectively. In patients who received IMRT, the1-, 2-, 3-year overall survival rates were 94.3%, 90.9% and 90.9% respectively; In patients who received CRT, the 1-, 2-, 3-year overall survival rates were 93.2%, 67.4% and 67.4% respectively. On univariate analysis, clinical stage, T and N stage were independent factors for overall survival. Analyzing the dose distribution of Target Volume in IMRT, the average volume which rec- eived more than 95% of the prescribed dose for GTVnx, GVTnd and CTV was 99.83%, 99.95% and 99.53%, HI was 1.03, 1.03 and 1.07 respectively. The conformity and uniformity of target volume in IMRT were much better than conventional radiotherapy, and the dose of normal tissue abroad was lower in IMRT. The dose delivered to ORA was well controlled in both IM- RT and CRT. When it came to toxicities, the incidence of acute xerostomia and acute dysphagia was significant lower in IMRT than in CRT. The incide- nce of acute cutaneous injury, acute mucositis and hematological toxicity was similar in two groups. The long-term xerostomia released significantly in the IMRT group while this phenomenon didn't happen in the CRT group.Conclusion:1. Radiotherapy is the prefer therapy in nasopharyngeal carcinoma, the short-term effect is positive.2. Intensity-modulated radiotherapy provided excellent tumor target coverage and allowed the delivery of a high dose to the target with signific- ant sparing of the nearby normal tissues. IMRT have the preponderance over CRT.3. Intensity-modulated radiotherapy may improve local-regional contr- ol rate, and overall survival rate could be raised.4. Local recurrence and distant metastases are now the major form of failure. Improvement of local-regional control rate in advanced stage patie- nts and decrease of distant metastases rate are fundamental factors.
|
PDF Full Text Request