title: High-risk factors of parotid lymph node metastasis in nasopharyngeal carcinoma: a case-control study.
abstract: BACKGROUND
  Although parotid-sparing IMRT decreased the dose distribution of parotid, parotid region recurrence has been reported. Prophylactic irradiation in parotid area would be necessary in patients with high risk of parotid lymph node metastasis (PLNM). This study was to detect the high-risk factors of PLNM in nasopharyngeal carcinoma.
  
  
  METHODS
  This was a 1:2 case-control study. All patients in this study were newly diagnosed NPC with N2-3 classification from January 2005 to December 2012. Cases were 22 sides with ipsilateral PLNM. Controls were 44 patients who were randomly selected from N2-3 disease in database.
  
  
  RESULTS
  20/1096 (1.82 %) NPC patients were found PLNM. Sum of the longest diameter for multiple lymph nodes (SLD) in level II was larger in case group than that in control group (6.0 cm vs. 3.6 cm, p = 0.003). Level II lymph node necrosis, level Va/b involvement, and rare neck areas involvement were more common in case group (p = 0.016, p = 0.034, and p < 0.001, respectively). RPN, level III, and level IV metastases showed no significant difference between the two groups. Multivariate analysis in logistic regression showed that only SLD ≥5 cm in II area (OR = 4.11, p = 0.030) and rare neck areas involvement (OR = 3.95, p = 0.045) were associated with PLNM in NPC patients.
  
  
  CONCLUSIONS
  PLNM was an uncommon event in NPC patients. SLD ≥5 cm in level II and involvement in rare-neck areas may be potentially high-risk factors for PLNM. Sparing parotid in IMRT was not recommended for NPC patients with high risks of PLNM.
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Hong-Zhi
authors: HZ
authors: Wang
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Cai-Neng
authors: CN
authors: Cao
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China. jingwei-luo@outlook.com.
authors: Jing-Wei
authors: JW
authors: Luo
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Jun-Lin
authors: JL
authors: Yi
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Xiao-Dong
authors: XD
authors: Huang
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Shi-Ping
authors: SP
authors: Zhang
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Kai
authors: K
authors: Wang
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Yuan
authors: Y
authors: Qu
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Jian-Ping
authors: JP
authors: Xiao
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Su-Yan
authors: SY
authors: Li
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Li
authors: L
authors: Gao
authors: Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Science, Peking Union Medical College, No.17 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, China.
authors: Guo-Zhen
authors: GZ
authors: Xu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002277:Carcinoma; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D012372:ROC Curve; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D012984:Software; D055815:Young Adult
keywords: Case-control study; Nasopharyngeal carcinoma; Periparotid lymph node metastasis; Risk factors