Objective: The aim of the current study was to evaluate the difference between clinical tumor size and pathologic tumor size and the influence of both parameters on cancer-specific survival in patients with renal cell carcinoma.
Materials and methods: Clinical tumor size was measured by CT in 834 patients undergoing nephrectomy and was compared with pathologic tumor size. Clinical tumor size and clinical tumor stages were assessed in a central radiologic review. Several variables were analyzed regarding their impact on cancer-specific survival by use of the Kaplan-Meier method, multivariable Cox regression, and receiver operating characteristic analysis.
Results: The mean duration of follow-up for patients who were alive at the end of the study (n = 564) was 85 months. The mean clinical and pathologic tumor size was 5.93 and 5.53 cm, respectively (p = 0.005). Of 265 patients with cT1a tumors, only 3.0% (n = 8) had pathologic tumor stage pT3a or higher. In contrast, 15.2% of 317 patients with cT1b tumors had pathologic tumor stage pT2 or higher. Five-year cancer-specific survival according to clinical tumor size was 94% (≤ 4 cm), 83% (4.01-7 cm), and 68% (> 7 cm), respectively (p < 0.001). Multivariable regression analysis revealed that metastasis, sex, age, and clinical tumor size significantly influenced cancer-specific survival. Integration of pathologic tumor size instead of clinical tumor size into multivariable analysis resulted in a reduction of predictive accuracy of 2.3%.
Conclusion: CT significantly overestimated tumor size in the overall study group, but this overestimation is unlikely to be of clinical importance regarding the decision about radical versus nephron-sparing surgery. However, clinical understaging in 15% of cT1b tumors should be considered in treatment decision making. Clinical tumor size had an independent impact on cancer-specific survival and revealed a higher prognostic value compared with pathologic tumor size.