Maximum tumor diameter is not an accurate predictor of renal cell carcinoma tumor volume

Objective. The aim of this study was determine whether maximal renal cell carcinoma (RCC) size can be used to accurately determine tumor volume. Material and methods. Following institutional review board approval, the study evaluated 2180 patients who had been surgically treated for clear-cell RCC between 1985 and 2006 who had data available on three tumor dimensions. Tumor volume (TV) was defined as (π/6 × Height × Length × Width). True tumor volume (TTV) was calculated using the three measurements from the pathology report in the volume formula above. Estimated tumor volume (ETV) was calculated using only the largest dimension utilizing the same formula. Results. Only 45 out of 2180 patients (2%) had equal values for all three tumor dimensions. The mean differences in ETV and TTV were 5.4 cm³ for pT1a tumors, 38 cm³ for pT1b tumors, 158 cm³ for pT2a tumors, 723 cm ³ for pT2b tumors, 305 cm³ for pT3 tumors and 583 cm ³ for pT4 tumors (p < 0.001 for all). Conclusions. An ETV based on maximal tumor size is a poor assessment of TTV among patients with RCC, which is more pronounced with larger tumors. Future efforts to incorporate information on tumor volume in prognostic algorithms should use TTV.