title: Optimal Treatment Decision for Brain Metastases of Unknown Primary Origin: The Role and Timing of Radiosurgery.
abstract: BACKGROUND
  Up to 15% of all patients with brain metastases have no clearly detected primary site despite intensive evaluation, and this incidence has decreased with the use of improved imaging technology. Radiosurgery has been evaluated as one of the treatment modality for patients with limited brain metastases. In this study, we evaluated the effectiveness of radiosurgery for brain metastases from unknown primary tumors.
  
  
  METHODS
  We retrospectively evaluated 540 patients who underwent gamma knife radiosurgery (GKRS) for brain metastases radiologically diagnosed between August 1992 and September 2007 in our institution. First, the brain metastases were grouped into metachronous, synchronous, and precocious presentations according to the timing of diagnosis of the brain metastases. Then, synchronous and precocious brain metastases were further grouped into 1) unknown primary; 2) delayed known primary; and 3) synchronous metastases according to the timing of diagnosis of the primary origin. We analyzed the survival time and time to new brain metastasis in each group.
  
  
  RESULTS
  Of the 540 patients, 29 (5.4%) presented precocious or synchronous metastases (34 GKRS procedures for 174 lesions). The primary tumor was not found even after intensive and repeated systemic evaluation in 10 patients (unknown primary, 34.5%); found after 8 months in 3 patients (delayed known primary, 1.2%); and diagnosed at the same time as the brain metastases in 16 patients (synchronous metastasis, 55.2%). No statistically significant differences in survival time and time to new brain metastasis were found among the three groups.
  
  
  CONCLUSIONS
  Identification of a primary tumor before GKRS did not affect the patient outcomes. If other possible differential diagnoses were completely excluded, early GKRS can be an effective treatment option for brain metastases from unknown primary tumor.
authors.affiliation: Department of Neurosurgery, Yonsei University Health System, Seoul, Korea.
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Han
authors.affiliation: Department of Neurosurgery, Yonsei University Health System, Seoul, Korea.; Gamma Knife Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Won Seok
authors.initials: WS
authors.lastname: Chang
authors.affiliation: Department of Neurosurgery, Yonsei University Health System, Seoul, Korea.; Gamma Knife Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Hyun Ho
authors.initials: HH
authors.lastname: Jung
authors.affiliation: Department of Neurosurgery, Yonsei University Health System, Seoul, Korea.; Gamma Knife Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Yong Gou
authors.initials: YG
authors.lastname: Park
authors.affiliation: Department of Neurosurgery, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Hae Yu
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Yonsei University Health System, Seoul, Korea.; Brain Tumor Center, Yonsei University Health System, Seoul, Korea.; Gamma Knife Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Jong Hee
authors.initials: JH
authors.lastname: Chang
keywords: Neoplasm metastasis; Neoplasms, Unknown primary; Radiosurgery