title: Renal cell carcinoma: A nomogram for the CT imaging-inclusive prediction of indolent, non-clear cell renal cortical tumours.
abstract: To develop a nomogram from clinical and computed tomography (CT) data for pre-treatment identification of indolent renal cortical tumours.
  
  
  
  A total of 1201 consecutive patients underwent dedicated contrast-enhanced CT prior to nephrectomy for a renal cortical tumour between January 2000 and July 2011. Two radiologists evaluated all tumours on CT for size, necrosis, calcification, contour, renal vein invasion, collecting system invasion, contact with renal sinus fat, multicystic tumour architecture, nodular enhancement, and the degree of nephrographic phase enhancement. CT and clinical predictors (gender, body mass index [BMI], age) were incorporated into the nomogram. We employed multivariable logistic regression analysis to predict tumour type and internally validated the final model using the data from reader 1. External validation was performed by using all data from reader 2. We applied Wilcoxon rank sum test and Fisher's exact test to investigate for differences in tumour size, BMI, age, and differences in CT imaging features between patients with aggressive and those with indolent tumours.
  
  
  
  63.6% (764/1201) of patients had clear-cell or other aggressive non-clear-cell RCC (i.e. papillary RCC type 2, unclassified RCC) and 36.4% (437/1201) had indolent renal cortical tumours (i.e. papillary RCC type 1, chromophobe RCC, angiomyolipoma, or oncocytoma). On CT, indolent tumours were significantly smaller (p < 0.001) than aggressive tumours and significantly associated with well-defined tumour contours (p < 0.001). Aggressive RCC were significantly associated with necrosis, calcification, renal vein invasion, collecting system invasion, contact with renal sinus fat, multicystic tumour architecture, and nodular enhancement (all, p < 0.001). The nomogram's concordance index (C-index) was 0.823 after internal and 0.829 after external validation.
  
  
  
  We present a nomogram based on 1201 patients combining CT features with clinical data for the prediction of indolent renal cortical tumours. When externally validated, this nomogram resulted in a C-index of 0.829.
authors.affiliation: Genitourinary Imaging Group, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA. Electronic address: Christoph.Karlo@usz.ch.
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Karlo
authors.affiliation: Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Kou
authors.affiliation: Genitourinary Imaging Group, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Pier Luigi
authors.initials: PL
authors.lastname: Di Paolo
authors.affiliation: Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Kattan
authors.affiliation: Genitourinary Oncology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Motzer
authors.affiliation: Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Russo
authors.affiliation: Genitourinary Pathology, Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Satish K
authors.initials: SK
authors.lastname: Tickoo
authors.affiliation: Genitourinary Imaging Group, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Oguz
authors.initials: O
authors.lastname: Akin
authors.affiliation: Genitourinary Imaging Group, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA.
authors.forename: Hedvig
authors.initials: H
authors.lastname: Hricak
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging* / Q000473:pathology; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D049451:Nomograms; D055815:Young Adult
keywords: Angiomyolipoma; CT; Chromophobe; Clear Cell; Computed Tomography; Nomogram; Oncocytoma; Papillary; RCC; Renal Cell Carcinoma