title: The role of tumor size in the radiosurgical management of patients with ambiguous brain metastases.
abstract: OBJECTIVE
  To identify a size cutoff below which it is safe to observe obscure brain lesions suspected of being metastases so that treatment of nonmetastases can be avoided.
  
  
  METHODS
  Medical records from patients who underwent linear accelerator-based radiosurgery from August 1991 to October 2001 were reviewed. Inclusion criteria were defined as brain metastasis tumor volume less than 5 cm(3) (diameter, thick similar 2.1 cm) treated with a dose of 20 Gy or more. One hundred thirty-five patients had 153 evaluable brain metastases with follow-up imaging that met inclusion criteria. Median age was 54 years (range, 18-79 yr). Lesion primaries were non-small-cell lung (n = 39), melanoma (n = 44), renal (n = 37), breast (n = 18), colon (n = 3), sarcoma (n = 5), other (n = 5), and unknown primary (n = 2). Median tumor volume was 0.67 cm(3) (range, 0.06-4.58 cm(3)). The minimum peripheral dose was 20 Gy (n = 132) or 21 to 24 Gy (n = 21). At the time of analysis, the median follow-up for all patients was 10 months (range, 0.2-99 mo).
  
  
  RESULTS
  The 1- and 2-year actuarial local control rates for all of the lesions were 69 and 46%, respectively. For lesions of 1 cm (0.5 cm(3)) or less, the corresponding local control rates were 86 and 78%, respectively, which was significantly higher than the corresponding rates of 56 and 24%, respectively, for lesions larger than 1 cm (0.5 cm(3)) (P = 0.0016).
  
  
  CONCLUSIONS
  A convincing brain metastasis measuring less than 1 cm should be pursued aggressively. If the suspected brain metastasis is ambiguous, observation is proposed up to a diameter of 1 cm. This is the first study in the literature to identify a 1-cm cutoff for radiosurgical control of small brain metastases, and validation by additional studies is required.
authors.affiliation: Division of Radiation Oncology, Brain Tumor Center, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA. echang@mdanderson.org
authors.forename: Eric L
authors.initials: EL
authors.lastname: Chang
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Hassenbusch
authors.forename: Almon S
authors.initials: AS
authors.lastname: Shiu
authors.forename: Frederick F
authors.initials: FF
authors.lastname: Lang
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Allen
authors.forename: Raymond
authors.initials: R
authors.lastname: Sawaya
authors.forename: Moshe H
authors.initials: MH
authors.lastname: Maor
mesh_terms: D000206:Actuarial Analysis; D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology* / Q000556:secondary / Q000601:surgery*; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D016634:Radiosurgery; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013997:Time Factors