CT Staging of Renal Cell Carcinoma Using the Revised 1997 TNM Staging Criteria: In Comparison with the Previous One

Sung, Deuk Jae; Kim, Yun Hwan; Chung, Hwan Hoon; Chung, Kyoo Byung; Suh, Won Hyuck

Abstract

PURPOSE: To assess the accuracy of preoperative CT staging of RCC and to compare the relationship between T stage and the incidence of metastasis on the basis of the old (1992) and the new (1997) UICC & AJCC tumor classification system.
MATERIALS AND METHODS
In 112 cases of surgically resected RCC, the stagings of preoperative CT scans were de-termined retrospectively by two radiologists and were compared with the results of pathologic examinations. In 70 cases which had been followed up over three years after surgery, the incidence of metastasis at initial diagnosis and during the follow-up period was assessed. All cases were reconsidered, and using the old and the new TNM classification, the incidence of metastasis was compared.
RESULTS
According to the old TNM classification, 5 cases (4%) were staged at T1, 73(65%) at T2, 21(19%) at T3a, 9(8%) at T3b, 0 at T3c, and 4(4%) at T4. Using the new TNM classification, we also staged 54 cases (48%) at T1 and 24(21%) at T2. Overall, using this new classification, CT correctly staged 79% of patients (88/112) overstaged 15%(17/112) and understaged 6%(7/112) . CT had a sensitivity of 84% and specificity of 91% in new T1 tumors, 71% and 95%, respectively, in new T2 tumors, 69% and 88% in T3a tumors, 78% and 98% in T3b tumors, and 75% and 99% in T4 tumors. CT had a sensitivity of 44% and a specificity of 99% in old T1 tumors, and 82% and 71%, respectively, in old T2 tumors. The incidence of metastasis in CT-staged (cT) tumors was 0% (0/4) in old cT1, 8% (3/39) in new cT1, 29% (4/14) in new cT2, 67% (6/9) in cT3a, and 75% (6/8) in cT3b.
CONCLUSION
In the staging of T1 tumors, CT is more sensitive when the new TNM classification is used. Even though the cut off point between T1 and T2 tumors had been in creased from 2.5 to 7.0 cm, T1 tumors staged according to the new system did not show a significantly higher incidence of metastasis than those staged according to the old.