title: Natural history, growth kinetics, and outcomes of untreated clinically localized renal tumors under active surveillance.
abstract: BACKGROUND
  The growth kinetics of untreated solid organ malignancies are not defined. Radiographic active surveillance (AS) of renal tumors in patients unfit or unwilling to undergo intervention provides an opportunity to quantify the natural history of untreated localized tumors. The authors report the radiographic growth kinetics of renal neoplasms during a period of surveillance.
  
  
  METHODS
  The authors identified patients with enhancing renal masses who were radiographically observed for at least 12 months. Clinical and pathological records were reviewed to determine tumor growth kinetics and clinical outcomes. Tumor growth kinetics were expressed in terms of absolute and relative linear and volumetric growth.
  
  
  RESULTS
  The authors identified 172 renal tumors in 154 patients under AS. Median tumor diameter and volume on presentation were 2.0 cm (mean, 2.5; range, 0.4-12.0) and 4.18 cm(3) (mean, 20.0; range, 0.033-904). Median duration of follow-up was 24 months (mean, 31; range, 12-156). A significant association between presenting tumor size and proportional growth was noted, with smaller tumors growing faster than larger tumors. Thirty-nine percent (68 of 173) of tumors underwent delayed intervention, and 84% (57 of 68) were pathologically malignant. Progression to metastatic disease was noted in 1.3% (2 of 154) of patients.
  
  
  CONCLUSIONS
  The authors demonstrated the association between a tumor's volume and subsequent growth, with smaller tumors exhibiting significantly faster volumetric growth than larger tumors, consistent with Gompertzian kinetics. Surveillance of localized renal tumors is associated with a low rate of disease progression in the intermediate term, and suggests potential overtreatment biases in select patients.
authors.affiliation: Section of Urologic Oncology, Department of Surgical Oncology, Fox Chase Cancer Center, Temple University Medical Center, Philadelphia, Pennsylvania, USA.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Crispen
authors.forename: Rosalia
authors.initials: R
authors.lastname: Viterbo
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Boorjian
authors.forename: Richard E
authors.initials: RE
authors.lastname: Greenberg
authors.forename: David Y T
authors.initials: DY
authors.lastname: Chen
authors.forename: Robert G
authors.initials: RG
authors.lastname: Uzzo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D019370:Observation; D011859:Radiography; D013997:Time Factors; D016896:Treatment Outcome; D047368:Tumor Burden