Difference Between Clinical and Pathologic Renal Tumor Size, Correlation With Survival, and Implications for Patient Counseling Regarding Nephron-Sparing Surgery

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.