67th Annual Meeting Abstracts

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Magnetic Resonance Imaging Better Predicts Pathologic Renal Tumor Size Prior to Radical or Partial Nephrectomy
Phillip Mucksavage¹, *Megan Mucksavage¹, Alexander Kutikov², Shawn White¹, Thomas Guzzo¹, Keith Van Arsdalen¹, S. Bruce Malkowicz^1
1University of Pennsylvania, Philadelphia, PA;²Fox Chase Cancer Center, Philadelphia, PA

Introduction: Magnetic resonance imaging (MRI), computed tomography (CT) and ultrasound are all reliable methods for determining renal tumor size. We examined which modality was best at determining pathologic tumor size prior to radical or partial nephrectomy for RCC.
Materials & Methods: The data of 776 patients who underwent radical or partial nephrectomy was reviewed. The maximum reported diameter of the tumor was compared to the maximum diameter of the tumor after resection. Benign lesions and patients with incomplete data were eliminated from analysis. Data was analyzed by paired student T-test, Spearman rank correlation and linear regression analysis.
Results: 647 patients had available data for analysis, including 385 CT scans, 112 ultrasounds, and 421 MRIs. Average time from imaging to surgery was 87.1 days. When tumor size was compared to preoperative size on ultrasound, CT, and MRI, there was no significant difference between the estimated preoperative tumor size and pathologic tumor size (Table 1.) Pathologic tumor size was well correlated with all three modalities (p<0.001). When all three modalities were performed in the same patient preoperatively, only MRI remained a significant predictor of tumor size in multivariable analysis.
Conclusions: All three standard renal imaging modalities appear to accurately predict pathologic tumor size in patients with primary malignant RCC. When comparing all three modalities against each other, MRI appears to perform better in predicting pathologic tumor size.

Table 1

Modality	Preoperative Tumor Size	Pathologic Tumor Size	Difference	p value*
Ultrasound (n=112)	4.76 cm	4.60 cm	-0.14cm (S.D = 2.48)	p = 0.54
Computed Tomography (n= 385)	4.93 cm	4.98 cm	0.05 cm (S.D = 1.84)	p =0.62
Magnetic Resonance (n= 421)	4.61 cm	4.67 cm	0.05cm (S.D = 1.78)	p = 0.56
* p value determined by paired Student T-test, S.D. = Standard Deviation

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