1. Can Renal Mass Features on CT Predict Positive Margins?
Nick N. Tadros, MD, Brian D. Duty, MD, Michael J. Conlin MD: Portland, OR
Oregon Health Sciences University, Portland VA Medical Center
World Congress of Endourology
October 22-26, 2013
Introduction
The C-Index, PADUA, and RENAL nephrometry scores are three standardized scoring systems commonly used to quantify renal mass complexity, primarily for the purpose of surgical planning. These scoring systems are based upon tumor size and location. They do not take into account tumor characteristics such as heterogeneity and shape. The purpose of our study was to determine if renal mass features on computed tomography (CT) can predict margin status in patients undergoing partial nephrectomy.
Tumor Heterogeneity
Visceral
Subcutaneous
Methods
This is a case-control study of patients treated by partial nephrectomy comparing patients with positive margins (cases) to those with negative margins (controls). Patients were identified from the Oregon Health & Science University tumor registry. OsiriX, an open source medical imaging application, was used to measure:
tumor heterogeneity (standard deviation of Hounsfiled units)
perinephric fat stranding
distinctness of the tumor/kidney interface (subjective scale)
tumor geometric complexity (measured surface area/calculated surface area of a sphere of the same volume)
percentage of visceral fat
Imaging characteristics of 15 individuals with positive margins were compared to 15 patients with negative margins.  
1.0
2.4
1.6
Geometric Complexity Index
Low Complexity
Higher Complexity
Results
Baseline demographics (age, gender), tumor size, RENAL nephrometry score, treatment modality (open versus laparoscopic) did not differ between the two groups. On univariable (Table 1) and multivariable (Table 2) analysis, no difference was found between the two groups with regard to tumor heterogeneity, perinephric fat stranding, distinctness of the tumor/kidney interface, tumor geometric complexity and percentage of visceral fat.
Univariable Analysis (Table 1)
(+) Margins
(-) Margins
P-value
Tumor Diameter (mm)
25.4
29.7
0.415
Procedure -
0.848
Nephrometry Score
6.0
6.72
0.322
Average Heterogeneity
74.12
77.74
0.745
Heterogeneity SD
27.26
29.04
0.714
Subjective Stranding
0.917
0.75
0.527
Average Stranding (HU)
-94.64
-77.14
0.214
Border Fuzziness
0.69
0.5
0.427
Viseral:total fat ratio
0.367
0.441
0.25
GCI
1.578
1.678
0.083
Multivariable Analysis (Table 2)
p-value
Tumor Diameter (mm)
0.315
Procedure
0.415
Nephrometry Score
0.318
Heterogeneity SD
0.878
Average Stranding (HU)
0.602
Border Fuzziness
0.407
Viseral:total fat ratio
0.327
GCI
0.099
Conclusions
Although no difference was found in tumor characteristics between patients with and without positive surgical margins, there was a trend towards significance for tumor geometric complexity (p= 0.099). We plan on expanding our sample size and evaluating geometric complexity as a predictor of pathologic (benign versus malignant, tumor subtype, tumor grade, and tumor stage) and surgical outcomes.