title: The role of perineural invasion on head and neck adenoid cystic carcinoma prognosis: a systematic review and meta-analysis.
abstract: OBJECTIVE
  We performed a systematic review to assess the prognostic value of perineural invasion (PNI) for patients with head and neck adenoid cystic carcinoma.
  
  
  METHODS
  A literature search of MEDLINE and EMBASE was used to identify relevant literature up to December 2015. The primary outcomes of interest were overall survival, disease-free survival, and locoregional control. Study information and hazard ratios (HRs) were extracted, and HRs were pooled using the Mantel-Haenszel fixed-effects model and the DerSimonian and Laird random-effects model according to heterogeneity.
  
  
  RESULTS
  Twenty-two studies and 1332 patients were included in this study. The PNI ratio was 43.2%. PNI was at increasing risk for overall survival (HR = 2.98; 95% confidence interval [CI] 2.00-4.46), disease-free survival (HR = 1.88; 95% CI, 1.42-2.49), and locoregional control (HR = 2.15; 95% CI, 1.48-3.13) with statistical significance.
  
  
  CONCLUSIONS
  PNI is an independent factor for poor prognosis in patients with head and neck adenoid cystic carcinoma. Moreover, PNI poses a significantly higher threat to male patients and younger patients.
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China; Navy General Hospital of Chinese PLA, Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ju
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Oral and Maxillofacial Surgery, Department of Stomatology, Xi'an Medical University, Xi'an, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Chai
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Qianwei
authors.initials: Q
authors.lastname: Ni
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, China. Electronic address: Moyisun@163.com.
authors.forename: Moyi
authors.initials: M
authors.lastname: Sun
mesh_terms: D003528:Carcinoma, Adenoid Cystic / Q000473:pathology*; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D009361:Neoplasm Invasiveness / Q000473:pathology*; D010524:Peripheral Nervous System Neoplasms / Q000473:pathology*; D011379:Prognosis; D012307:Risk Factors