MRI for Preoperative Staging of Renal Cell Carcinoma Using the 1997 TNM Classification: Comparison with Surgical and Pathologic Staging

OBJECTIVE. The purpose of our study was to determine the accuracy of MRI for preoperative staging of renal cell carcinoma using the 1997 TNM classification. MATERIALS AND METHODS. We conducted a retrospective review of MRI performed in 40 consecutive patients with 42 renal cell carcinomas before radical (n = 35) or partial (n = 4) nephrectomy or exploratory laparotomy (n = 3). The interval between imaging and surgery ranged from 1 to 59 days (mean, 17.9 days). Imaging was performed with T1- and T2-weighted, dynamic gadolinium-enhanced, and time-of-flight sequences. MRI and surgical-pathologic staging was performed using the 1997 TNM staging system. MRI staging was compared with surgical-pathologic staging as the gold standard. Agreement between the two staging methods was assessed using the kappa statistic. RESULTS. Agreement between MRI and surgical-pathologic staging was good for T staging (κ = 0.72 and 0.78 for reviewers 1 and 2 respectively), poor for N staging (κ = 0.13, both reviewers), good for M staging (κ = 0.66, both reviewers), and excellent for the assessment of venous involvement (κ = 0.93, both reviewers). MRI overestimated the T stage in five patients and the N stage in five and underestimated the T stage in three, the N stage in four, the M stage in one, and the extent of venous thrombosis in two patients. CONCLUSION. MRI is a reliable method for preoperative staging of renal cell carcinoma using the 1997 TNM classification, in particular for assessing venous involvement.