title: Growth kinetics of small renal masses: A prospective analysis from the Renal Cell Carcinoma Consortium of Canada.
abstract: BACKGROUND
  Most small renal masses (SRMs) are diagnosed incidentally and have a low malignant potential. As more elderly patients and infirm patients are diagnosed with SRMs, there is an increased interest in active surveillance (AS) with delayed intervention. Patient and tumour characteristics relating to aggressive disease have not been well-studied. The objective was to determine predictors of growth of SRMs treated with AS.
  
  
  METHODS
  A multicentre prospective phase 2 clinical trial was conducted on 207 SRMs in 169 patients in 8 institutions in Canada from 2004 to 2009; in these patients treatment was delayed until disease progression. Patient and tumour characteristics were evaluated to determine predictors of growth of SRMs by measuring rates of change in growth (on imaging) over time. All patients underwent AS for presumed renal cell carcinoma (RCC) based on diagnostic imaging. We used the following factors to develop a predictive model of tumour growth with binary recursive partitioning analysis: patient characteristics (age, symptoms at diagnosis) and tumour characteristics (consistency [solid vs. cystic] and maximum diameter at diagnosis.
  
  
  RESULTS
  With a median follow-up of 603 days, 169 patients (with 207 SRMs) were followed prospectively. Age, symptoms at diagnosis, tumour consistency and maximum diameter of the renal mass were not predictors of growth. This cohort was limited by lack of availability of patient and tumour characteristics, such as sex, degree of endophytic component and tumour location.
  
  
  CONCLUSIONS
  Slow growth rates and the low malignant potential of SRMs have led to AS as a treatment option in the elderly and infirm population. In a large prospective cohort, we have shown that age, symptoms, tumour consistency and maximum diameter of the mass at diagnosis are not predictors of growth of T1a lesions. More knowledge on predictors of growth of SRMs is needed.
authors.affiliation: Faculty of Medicine, Department of Urology, Dalhousie University, Halifax, NS;
authors.forename: Michael
authors.initials: M
authors.lastname: Organ
authors.affiliation: Department of Surgery, Division of Urology, University of Toronto, Toronto, ON; Kidney Cancer Research Network of Canada, Toronto, ON;
authors.forename: Michael
authors.initials: M
authors.lastname: Jewett
authors.affiliation: Faculty of Medicine, Department of Urology, Dalhousie University, Halifax, NS;
authors.forename: Joan
authors.initials: J
authors.lastname: Basiuk
authors.affiliation: Department of Surgery, Division of Urology, University of Ottawa, Ottawa, ON;
authors.forename: Christopher
authors.initials: C
authors.lastname: Morash
authors.affiliation: Division of Urology, Schulich School of Medicine and Dentistry, Western University, London, ON;
authors.forename: Stephen
authors.initials: S
authors.lastname: Pautler
authors.affiliation: Department of Urology, Queen's University, Kingston, ON;
authors.forename: D Robert
authors.initials: DR
authors.lastname: Siemens
authors.affiliation: Division of Urology, McGill University, Montreal, QC;
authors.forename: Simon
authors.initials: S
authors.lastname: Tanguay
authors.affiliation: Department of Urologic Sciences, University of British Columbia, Vancouver, BC;
authors.forename: Martin
authors.initials: M
authors.lastname: Gleave
authors.affiliation: Faculty of Medicine, Division of Urology, University of Manitoba, Winnipeg, MB;
authors.forename: Darrell
authors.initials: D
authors.lastname: Drachenberg
authors.affiliation: Department of Health Informatics, Princess Margaret Hospital, Toronto, ON;
authors.forename: Raymond
authors.initials: R
authors.lastname: Chow
authors.affiliation: Division of Urology, Schulich School of Medicine and Dentistry, Western University, London, ON;
authors.forename: Joseph
authors.initials: J
authors.lastname: Chin
authors.affiliation: Department of Pathology and Laboratory, Faculty of Medicine, University of Toronto, Toronto, ON;
authors.forename: Andrew
authors.initials: A
authors.lastname: Evans
authors.affiliation: Department of Surgery, Division of Urology, University of Toronto, Toronto, ON; Kidney Cancer Research Network of Canada, Toronto, ON;
authors.forename: Neil
authors.initials: N
authors.lastname: Fleshner
authors.affiliation: Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, ON;
authors.forename: Brenda
authors.initials: B
authors.lastname: Gallie
authors.affiliation: Department of Medical Imaging, University of Toronto, Toronto, ON.
authors.forename: Masoom
authors.initials: M
authors.lastname: Haider
authors.affiliation: Department of Medical Imaging, University of Toronto, Toronto, ON.
authors.forename: John
authors.initials: J
authors.lastname: Kachura
authors.affiliation: Department of Surgery, Division of Urology, University of Toronto, Toronto, ON; Kidney Cancer Research Network of Canada, Toronto, ON;
authors.forename: Antonio
authors.initials: A
authors.lastname: Finelli
authors.affiliation: Faculty of Medicine, Department of Urology, Dalhousie University, Halifax, NS;
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Rendon