Dosimetry And Short Term Outcomes Of Intensity Modulated Radiation Therapy For Retropharyngeal Lymph Lymph Node In Nasopharyngeal Carcinoma

Objective: To explore the relationship of intensity modulated radiationtherapy dose for retropharyngeal lymph node (RLN) in nasopharyngealcarcinoma (NPC) and short-term effects,and to provide a reference for settingreasonable dose of nasopharyngeal pharyngeal lymph nodes.Methods: From January2012to January2013,140NPC patients withpositive RLN received intensity modulated radiation therapy using theprescribed dose of PGTVrpn:2.10~2.25Gy/time,5times/week, total dose:66~76Gy/6~7weeks. The biological effective dose (BED) of RLN wascalculated by the actual dose of RLN and Linear-quatraticformulation. Take therecent evaluation of the efficacy of radiotherapy, at the end of radiotherapy,3months,6months and12months after radiotherapy, the radiotherapy efficacy ofRLN were recorded as complete remission (CR) and partial remission (PR).Results:(1) The complete remission rates of RLN at the end ofradiotherapy,3months and6months after radiotherapy were55.7%,75%, 87.2%, respectively. The difference were statistically significant (P<0.05). Thecomplete remission rate of RLN at12months after radiotherapy was93.5%.Compared with6months after radiotherapy, the complete remission rate was notsignificant different (P>0.05).(2) At the end of radiotherapy,3months,6months and12months after radiotherapy, the BED of RLN between thecomplete remission group and the partial remission group were not statisticallysignificant (P>0.05).(3) According to the median BED,the subjects weredivided into high BED group and low BED group. At four stages afterradiotherapy, the BED of RLN between the complete remission group and thepartial remission group were not statistically significant (P>0.05).(4) At the endof radiotherapy,3months,6months and12months after radiotherapy, the targetvolume of RLN between the complete remission group and the partial remissiongroup were not statistically significant (P>0.05),the target volume of RLN ofcomplete remission group is larger.Conclusion: The radiotherapy efficacy of RLN should be evaluated at6months after radiotherapy. If radiation dose of RLN reachs radical therapydose, no benefit is gained when improve localized radiation dose. RLN beforeradiotherapy volume size is an important influence its CR rate.