title: Whole lesion quantitative CT evaluation of renal cell carcinoma: differentiation of clear cell from papillary renal cell carcinoma.
abstract: OBJECTIVE
  Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell cancer (RCC), followed by papillary RCC (pRCC). It is important to distinguish these two subtypes because of prognostic differences and possible changes in management, especially in cases undergoing active surveillance. The purpose of our study is to evaluate the use of voxel-based whole-lesion (WL) enhancement parameters on contrast enhanced computed tomography (CECT) to distinguish ccRCC from pRCC.
  
  
  METHODS
  In this institutional review board-approved study, we retrospectively queried the surgical database for post nephrectomy patients who had pathology proven ccRCC or pRCC and who had preoperative multiphase CECT of the abdomen between June 2009 and June 2011. A total of 61 patients (46 with ccRCC and 15 with pRCC) who underwent robotic assisted partial nephrectomy for clinically localized disease were included in the study. Multiphase CT acquisitions were transferred to a dedicated three-dimensional workstation, and WL regions of interest were manually segmented. Voxel-based contrast enhancement values were collected from the lesion segmentation and displayed as a histogram. Mean and median enhancement and histogram distribution parameters skewness, kurtosis, standard deviation, and interquartile range were calculated for each lesion. Comparison between ccRCC and pRCC was made using each imaging parameter. For mean and median enhancement, which had a normal distribution, independent t-test was used. For histogram distribution parameters, which were not normally distributed, Wilcoxon rank sum test was used.
  
  
  RESULTS
  ccRCC had significantly higher mean and median whole WL enhancement (p < 0.01) compared to pRCC on arterial, nephrographic, and excretory phases. ccRCC had significantly higher interquartile range and standard deviation (p < 0.01) and significantly lower skewness (p < 0.01) compared to pRCC on arterial and nephrographic phases. ccRCC had significantly lower kurtosis compared to pRCC on only the arterial phase.
  
  
  CONCLUSIONS
  Our study suggests that voxel-based WL enhancement parameters can be used as a quantitative tool to differentiate ccRCC from pRCC. Differentiating between the two main types of RCC would provide the patient and the treating physicians more information to formulate the initial approach to managing the patient's renal cancer.
authors.affiliation: University of Southern California, 1500 San Pablo St, 2nd Floor Imaging, Los Angeles, CA 90033 USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Chen
authors.affiliation: University of Southern California, 1500 San Pablo St, 2nd Floor Imaging, Los Angeles, CA 90033 USA.
authors.forename: Hannu
authors.initials: H
authors.lastname: Huhdanpaa
authors.affiliation: University of Southern California, 1510 San Pablo St, Suite 350, Los Angeles, CA 90033 USA.
authors.forename: Bhushan
authors.initials: B
authors.lastname: Desai
authors.affiliation: University of Southern California, 1520 San Pablo St, Suite 4600, Los Angeles, CA 90033 USA.
authors.forename: Darryl
authors.initials: D
authors.lastname: Hwang
authors.affiliation: University of Southern California, SSB 210B, Health Sciences Campus, Los Angeles, CA 90089 USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Cen
authors.affiliation: University of Southern California, Health Sciences Campus, UNH 215, Los Angeles, CA 90089 USA.
authors.forename: Andy
authors.initials: A
authors.lastname: Sherrod
authors.affiliation: University of Southern California, 1441 Eastlake Avenue, NOR 7416, Los Angeles, CA 90033 USA.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Bernhard
authors.affiliation: University of Southern California, 1441 Eastlake Avenue, NOR 7416, Los Angeles, CA 90033 USA.
authors.forename: Mihir
authors.initials: M
authors.lastname: Desai
authors.affiliation: University of Southern California, 1441 Eastlake Avenue, NOR 7416, Los Angeles, CA 90033 USA.
authors.forename: Inderbir
authors.initials: I
authors.lastname: Gill
authors.affiliation: University of Southern California, 1441 Eastlake Avenue, NOR 2315, Los Angeles, CA 90033 USA.
authors.forename: Vinay
authors.initials: V
authors.lastname: Duddalwar
keywords: Clear cell renal cell carcinoma; Histogram analysis; Papillary renal cell carcinoma; Whole lesion enhancement parameters