title: Natural History of Renal Angiomyolipoma (AML): Most Patients with Large AMLs >4cm Can Be Offered Active Surveillance as an Initial Management Strategy.
abstract: The natural history of renal angiomyolipoma (AML) is unknown. Treatment recommendations are based on smaller case series, with selection bias towards symptomatic patients.
  
  
  
  To define the natural history of renal AML, including growth rates, size, and clinical presentation.
  
  
  
  We used a unique radiology data-mining system (Montage; Montage Healthcare Systems, Philadelphia, PA, USA) to retrospectively review the radiology database in an academic health centre between 2002 and 2013 to identify all renal AMLs. Of 2741 patients identified, 447 with 582 AMLs had three or more imaging studies suitable for analysis.
  
  
  
  Angioembolisation, surgery, radiofrequency ablation, and mammalian target of rapamycin inhibitors.
  
  
  
  The primary end point was the growth rate of untreated AMLs. We used a linear mixed-effects model to determine change in growth rate over time. We evaluated the association among growth rate, size, and patient factors as well as interventions.
  
  
  
  The majority of untreated AMLs (>92%) had not grown at a median follow-up of 43 mo, with no difference in growth rates between AMLs ≤4 and >4cm. Most AMLs occurred in female participants (80%) and were asymptomatic (91%). Tuberous sclerosis complex (TSC) was confirmed in 3.8% (n=17) and presented at an earlier age. Median size was 1cm but was significantly larger for TSC (5.5cm; p<0.001). Interventions were performed in 5.6% of patients. Limitations of our study include the retrospective design, selection against fat-poor AMLs, and lack of histology.
  
  
  
  This large, single-institution series on AMLs confirms that lesions >4cm do not require early intervention based on size alone. The vast majority are sporadic, asymptomatic, and initially harmless, with a negligible growth rate. Our findings support a policy of initial active surveillance for all asymptomatic AMLs.
  
  
  
  We evaluated the natural history and growth rates of renal AMLs. We found no difference in growth rates between AMLs >4 and ≤4cm. Initial AS appears to be a safe management option.
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada; Department of Urology, University Hospital Ayr, Scotland, UK.
authors.forename: Jaimin R
authors.initials: JR
authors.lastname: Bhatt
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Patrick O
authors.initials: PO
authors.lastname: Richard
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nicole S
authors.initials: NS
authors.lastname: Kim
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Antonio
authors.initials: A
authors.lastname: Finelli
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Manickavachagam
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Legere
authors.affiliation: Department of Pathology, Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Evans
authors.affiliation: Department of Medicine, Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: York
authors.initials: Y
authors.lastname: Pei
authors.affiliation: Department of Biostatistics, Princess Margaret Cancer Centre, University Health Network, and the University of Toronto.
authors.forename: Jenna
authors.initials: J
authors.lastname: Sykes
authors.affiliation: Joint Department of Medical Imaging, Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kartik
authors.initials: K
authors.lastname: Jhaveri
authors.affiliation: Departments of Surgical Oncology and Surgery (Urology), Princess Margaret Cancer Centre, University Health Network, and the University of Toronto, Toronto, Ontario, Canada. Electronic address: m.jewett@utoronto.ca.
authors.forename: Michael A S
authors.initials: MAS
authors.lastname: Jewett
mesh_terms: D000293:Adolescent; D000328:Adult; D000359:Aftercare; D000368:Aged; D000369:Aged, 80 and over; D018207:Angiomyolipoma / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D058070:Asymptomatic Diseases; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014402:Tuberous Sclerosis / Q000150:complications; D047368:Tumor Burden; D057832:Watchful Waiting; D055815:Young Adult
keywords: >4cm; Active surveillance; Large size; Renal angiomyolipoma