Comparison of diagnostic performance of CT and MRI for abdominal staging of pediatric renal tumors: a report from the Children's Oncology Group

Abstract

Background: CT and MRI are both used for abdominal staging of pediatric renal tumors. The diagnostic performance of the two modalities for local and regional staging of renal tumors has not been systematically evaluated.

Objective: To compare the diagnostic performance of CT and MRI for local staging of pediatric renal tumors.

Materials and methods: The study population was derived from the AREN03B2 study of the Children's Oncology Group. Baseline abdominal imaging performed with both CT and MRI within 30 days of nephrectomy was available for retrospective review in 82 renal tumor cases. Each case was evaluated for capsular penetration, lymph node metastasis, tumor thrombus, preoperative tumor rupture, and synchronous contralateral lesions. The surgical and pathological findings at central review were the reference standard.

Results: The sensitivity of CT and MRI for detecting capsular penetration was 68.6% and 62.9%, respectively (P = 0.73), while specificity was 86.5% and 83.8% (P = 1.0). The sensitivity of CT and MRI for detecting lymph node metastasis was 76.5% and 52.9% (P = 0.22), and specificity was 90.4% and 92.3% (P = 1.0). Synchronous contralateral lesions were identified by CT in 4/9 cases and by MRI in 7/9 cases.

Conclusion: CT and MRI have similar diagnostic performance for detection of lymph node metastasis and capsular penetration. MR detected more contralateral synchronous lesions; however these were present in a very small number of cases. Either modality can be used for initial loco-regional staging of pediatric renal tumors.

Fig. 1

Capsular penetration of Wilms tumor in a 7-year-old boy. Axial CT (a) and MRI (b) images show focal protrusion (arrows) of the renal mass beyond the renal capsule. This was pathologically confirmed to be capsular penetration

Fig. 2

Lymph node metastasis secondary to Wilms tumor in a 4-year-old boy. Axial CT (a) and MRI (b) images show enlarged retroperitoneal lymph node (arrow). Pathology confirmed lymph node metastasis, indicating stage III disease and a need for abdominal radiation

Fig. 3

Contralateral synchronous lesion in a 6-month-old girl with recently diagnosed Wilms tumor. Axial CT (a) and T2-weighted MRI (b) images. MRI shows a 1.2-cm T2-hyperintense lesion in the superior pole of the left kidney (arrow) which may represent a nephrogenic rest vs. contralateral Wilms tumor. This would upstage the patient to stage V. The lesion is poorly visualized on CT and was not detected prospectively on CT