title: Prevalence of known and unknown primary tumor sites in spinal metastasis patients.
abstract: METHODS
  A retrospective study.
  
  
  OBJECTIVE
  THREE OBJECTIVES HAVE BEEN DESIGNATED FOR THIS STUDY: (1) to determine the prevalence of identifiable and non-identifiable primary tumor sites in patients with spinal metastasis, (2) to identify the most common site of the known primary tumor sites, and (3) to identify the factors associated with survival time.
  
  
  BACKGROUND
  The spine is the third most common metastatic site for several primary visceral carcinomas. The primary tumor site could not be identified in 15% to 20% of patients who had been diagnosed of with a skeletal metastasis. Most of the previous studies on skeletal metastasis have not been limited to spinal metastasis alone.
  
  
  METHODS
  Between January 2007 and July 2011 reviews were done for 82 patients with spinal metastasis who had not received a previous diagnosis of carcinoma. The assessment parameters included the following: general demographic data, Karnofsky score, Frankel score, number of spinal vertebra affected, region of the spine affected by metastasis, other skeletal metastasis site, visceral metastasis, known or unknown primary sites of metastasis, histological cell type of metastasis, and the survival period. The log-rank test and Cox proportional hazard model were used to study the survival analysis.
  
  
  RESULTS
  Of the 82 patients included in the study, 56 were male. The mean age was 57 years. 86.6% had a known primary carcinoma site while the remaining 13.4% had none. The two most common known carcinoma sites were the lung and biliary systems. Among the 11 unknown primary sites, the most common histological finding was adenocarcinoma. The mean survival period was 8.7 ± 11.7 months. The survival analysis revealed two statistically significant factors: the primary tumor site's aggressiveness (P<0.005) and the presence of visceral metastasis (P<0.05).
  
  
  CONCLUSIONS
  The prevalence of identifiable primary site was 86.6% and the most common site was the lungs followed by the biliary system. The primary carcinoma site's aggressiveness and the presence of visceral metastasis were the factors associated with patient survival.
authors.affiliation: Department of Orthopedics, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.
authors.forename: Permsak
authors.initials: P
authors.lastname: Paholpak
authors.forename: Winai
authors.initials: W
authors.lastname: Sirichativapee
authors.forename: Taweechok
authors.initials: T
authors.lastname: Wisanuyotin
authors.forename: Weerachai
authors.initials: W
authors.lastname: Kosuwon
authors.forename: Polasak
authors.initials: P
authors.lastname: Jeeravipoolvarn
keywords: Spinal metastasis; cholangiocarcinoma; known primary tumor; survival analysis.; unknown primary tumor