title: Predictors of Delayed Intervention for Patients on Active Surveillance for Small Renal Masses: Does Renal Mass Biopsy Influence Our Decision?
abstract: OBJECTIVE
  To review our clinical T1a renal mass active surveillance (AS) cohort to determine whether renal mass biopsy was associated with maintenance of AS.
  
  
  METHODS
  From our prospectively maintained database we identified patients starting AS from June 2009 to December 2011 who had at least 5 months of radiologic follow-up, unless limited by unexpected death or delayed intervention. The primary outcome was delayed intervention. Clinical, radiologic, and pathologic variables were compared. We constructed Kaplan-Meier survival curves for maintenance of AS. Cox multivariable regression analysis was performed to assess predictors of delayed intervention.
  
  
  RESULTS
  We identified 118 patients who met criteria for inclusion with a median radiologic follow-up of 29.5 months. The delayed intervention group had greater initial mass size and faster growth rate compared to those who continued AS. Rate of renal mass biopsy was similar between the 2 groups. In the multivariable analysis, size >2 cm (hazard ratio [HR] 3.65, 95% confidence interval [CI] 1.28-10.38, P = .015), growth rate (continuous by mm/year: HR 1.26, 95% CI 1.12-1.41, P < .001), but not renal biopsy (HR 1.52, 95% CI 0.70-3.30, P = .29), were associated with increased risk of delayed intervention. Time-to-event curves also showed that size was closely associated with delayed intervention whereas renal mass biopsy was not.
  
  
  CONCLUSIONS
  At our institution, growth rate and initial tumor size appear to be more influential than renal mass biopsy results in determining delayed intervention after a period of AS. Further analysis is required to determine the role of renal biopsy in the management of patients being considered for AS.
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI. Electronic address: sapan@med.umich.edu.
authors.forename: Sapan N
authors.initials: SN
authors.lastname: Ambani
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Morgan
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Montgomery
authors.affiliation: Department of Urology, University of California-San Francisco, San Francisco, CA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Gadzinski
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA.
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Jacobs
authors.affiliation: University of Michigan Medical School, Ann Arbor, MI.
authors.forename: Scott
authors.initials: S
authors.lastname: Hawken
authors.affiliation: University of Michigan Medical School, Ann Arbor, MI.
authors.forename: Naveen
authors.initials: N
authors.lastname: Krishnan
authors.affiliation: Department of Radiology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Caoili
authors.affiliation: Department of Radiology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: James H
authors.initials: JH
authors.lastname: Ellis
authors.affiliation: Department of Pathology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Lakshmi P
authors.initials: LP
authors.lastname: Kunju
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Khaled S
authors.initials: KS
authors.lastname: Hafez
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: David C
authors.initials: DC
authors.lastname: Miller
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Ganesh S
authors.initials: GS
authors.lastname: Palapattu
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: Alon Z
authors.initials: AZ
authors.lastname: Weizer
authors.affiliation: Department of Urology, University of Michigan Health System, Ann Arbor, MI.
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Wolf
mesh_terms: D000368:Aged; D001706:Biopsy; D002292:Carcinoma, Renal Cell / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D000066491:Clinical Decision-Making; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007680:Kidney Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D008297:Male; D009367:Neoplasm Staging; D009392:Nephrectomy; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D047368:Tumor Burden; D014481:United States / Q000453:epidemiology; D057832:Watchful Waiting / Q000379:methods*