| Purpose:We spared level Ib lymph nodes by Intensity-Modulated Radiotherapy in the treatment of nasopharyngeal carcinoma patients and observed regional control related curative effect and dry mouth related toxicity, to evaluate the feasibility of no prophylactic irradiation to level Ib lymph nodes.Methods:We respectively recruited 193 nasopharyngeal carcinoma patients received treatment with level Ib lymph nodes spared by IMRT between January 2005 and December 2009 in our center. Before treatment, each patient underwent comprehensive stage image examination excluding level Ib lymph nodes involvement. Patients with negative cervical lymph nodes received radiotherapy to the nasopharynx, skull base and upper neck drainage areas including level II, III, VA lymph nodes, while patients with cervical lymph node involvement received treatment to the whole neck including level II-V lymph nodes. All patients had no level Ib prophylactic irradiation. The prescription doses were 66-70.4Gy/30-32 fractions to the gross tumor volume of nasopharynx and the positive neck nodes, while 54-60Gy/30-32 fractions to the subclinical region and lymphatic drainage area. We strictly limited the dose to submandibular gland of only 10 patients in our group referring to the standard of the parotid gland, which was defined as limited group. We selected another 10 patients matched according to the same TNM stage from the patients without dose limit to submandibular gland in our group, which was defined as non-limited group. We analysed the dose distribution of the submandibular gland, other organs at risk and tumor target between two groups. Dry mouth and other late toxicity were assessed according to the RTOG criteria, and evaluated the patterns of locoregional relapse and survival of patients combining with the history, symptom, examination.Results:The median age of 193 patients included was 49 years (20-73 years), the median follow-up period was 58 months (7-100 months). There is no significant difference about the dose distribution of tumor target and organ at risk between limited group and non-limited group, while the dose to submandibular gland (SMG) in limited group is significantly lower. The D50 of left SMG are 49.4Gy,56.9Gy, lower 7.5Gy (13.2%). The Dmean of left SMG are 48.5Gy,56.4Gy, lower 7.9Gy (14%). The D50 of right SMG are 49Gy, 57.2Gy, lower 8.2Gy(14.3%). The Dmean of right SMG are 49.1Gy,56.9Gy, lower 7.8Gy (13.7%). The percentage of volume receiving less than 39Gy on left and right SMG are 21.6% and 28.9% in limited group, while they are 6.4% and 0.2% in non-limited group. Through reexamination after radiotherapy, residual disease in nasopharynx and neck is 20.2%(39/193), 18.7%(36/193), respectively.2 patients staged T2 with pharyngonasal cavity residual each had additionally brachytherapy 8Gy.1 patient with neck residual was added external irradiation 4.4Gy/2F.26 patients suffered metastases,15 patients had local recurrence and 8 patients experienced regional recurrence without any recurrence in level Ib lymph node during long follow-up. The 5-year local control, regional control, distant metastasis-free and overall survival rates were 92.8%,95.9%, 85.8% and 83.9%, respectively. Dry mouth was still the common late adverse event with lower grade, only one patient experienced 3 grade xerostomia.Conclusion:1.The incidence of dry mouth was still high under Intensity-modulated radiation therapy, while lower grade than routine radiotherapy.2. Treatment without prophylactic irradiation to level Ib did not increase the risk of regional recurrence, or impact on local/regional control and overall survival in the long term follow-up. 3. Maintenance submandibular gland by lowering the dose to gland is feasible under intensity-modulated radiation therapy in NPC. Proper dose constraints for SMG require further studies with a larger sample size, and dose-effect relationship could be established combined with the results of subjective and objective evaluation of dry mouth. |
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