Three-dimensional tumour volume and cancer-specific survival for patients undergoing nephrectomy to treat pT1 clear-cell renal cell carcinoma

Abstract

Study Type - Prognosis (case series) Level of Evidence 4. What's known on the subject? and What does the study add? The positive association of tumour size (largest tumour dimension on pathology review) and risk of RCC progression and survival following nephrectomy is well documented. Moreover, several clinicopathological scoring systems (i.e. nomograms and algorithms) have been developed to predict outcomes for surgically treated RCC patients and each of these includes tumour size as an independent predictor of RCC outcome. There is still the question of whether information on three-dimensional tumour volume (cm(3) ) can provide additional prognostic information, particularly among patients with small pT1 tumours where the range of tumour size is more limited. Our study demonstrates that increasing tumour volume is associated with a greater risk of RCC-specific death in patients with pT1 ccRCC, with a more pronounced association in pT1a tumours specifically. In addition, we observed evidence that tumour volume may provide more accurate prognostic information than tumour size alone in pT1a patients. Tumour volume may add prognostic information specifically in pT1a RCC.

Objective: To address whether information on three-dimensional tumour volume can provide additional prognostic information for patients with small, localized renal cell carcinoma (RCC) superior to tumour size alone.

Patients and methods: We identified 955 patients treated with radical nephrectomy or nephron-sparing surgery for unilateral, sporadic, pT1, pN0/NX, M0, non-cystic clear-cell RCC (ccRCC) between 1980 and 2004, including 515 pT1a patients and 440 pT1b patients. • We estimated tumour volume using three tumour dimensions recorded on pathological analysis and the equation for the volume of an ellipsoid [π/6 (length × width × height)]. For tumour size alone, we used the maximum tumour diameter recorded on pathological analysis. • Univariate and multivariable associations with RCC-specific death were evaluated using Cox proportional hazards regression models summarized with hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: Among pT1a patients, the risk of RCC death associated with having a tumour volume above the median (HR = 4.55; 95% CI, 1.30-15.83; P= 0.018) was markedly higher than having a tumour size above the median (HR = 2.55; 95% CI 0.83-7.85; P= 0.10). Comparison of concordance (c) index values further supported the idea that additional prognostic information was provided by tumour volume (c= 0.659) compared with tumour size (c= 0.600) for pT1a patients. • Among pT1b patients, we noted that associations of tumour volume and tumour size with RCC-specific death were similar. • Multivariable adjustment did not alter our findings.

Conclusions: Tumour volume could provide valuable prognostic information for patients with pT1a ccRCC but not pT1b ccRCC. • Future investigations are needed to confirm this finding, explore other RCC subtypes and evaluate accuracy of tumour volume determination on radiographic imaging for potential patient management before surgery.