Introduction:

Preoperative assessment of T3a renal cell carcinoma (RCC) in the absence of obvious main renal vein involvement is challenging but may have important implications for prognosis and management. Upstaging of cT1-2 tumors to pT3a occurs in 10-20% of cases and associates with worse outcomes. Previous analyses have attempted to identify characteristics that may help predict pT3a status but, notably, imaging features have generally not been incorporated into these studies. The objective of this study was to evaluate various imaging characteristics suggestive of aggressive tumor biology or invasive phenotype and assess potential correlation with pT3a status among patients undergoing renal cancer surgery.

Methods:

A retrospective review of all cT1-T3aN0M0 RCC patients without radiological evidence of main renal vein involvement or substantial lymphadenopathy (excluded if LN burden >1.5cm) managed with partial or radical nephrectomy in our institution (2012-2014, n=1129) was performed.  All images were reviewed to define radiologic features blinded to final pathology. Eleven factors were assessed for possible correlation with pT3a status, including perinephric features (stranding, enhancing nodule, collateral vessels, or irregular-perinephric-tumor-contour), findings within the sinus [stranding, collecting system invasion, branch-vein enlargement, or irregular-tumor-sinus-border (ITSB)], tumor necrosis, infiltrative features, and tumor size. Sensitivity/specificity and logistic-regression analyses were performed to assess the performance of each imaging characteristic for detecting pT3a tumors. 

Results:

Median tumor size was 4.0 cm and R.E.N.A.L. was 8. Median follow-up was 53 months (IQR 28-64 months). pT3a tumors were found in 281 patients (25%) and strongly correlated with increased risk of local and systemic recurrence (p<0.02 for both). ITSB was found in 350 patients (31%) and proved to be the strongest predictor of pT3a status. Sensitivity/specificity/PPV/NPV/OR/C-Index for ITSB were 75%/84%/61%/91%/15.8(IQR 11.4-21.9)/0.80, for correlation with pT3a, respectively. Tumor size, which has the benefit of being an objective variable, had the second highest predictive value (C-index=0.76). The best predictive model for pT3a included ITSB and tumor size as a continuous variable (C-index=0.84). Addition of other imaging features did not improve the model (C-index remained 0.84). ITSB was the strongest contributor in all multivariable-models and also strongly correlated with recurrence free survival [HR (95% CI): 5.51 (3.61-8.41)]. Inter/intra-observer correlations for ITSB were 0.89/0.98, respectively.  Limitations include retrospective design. 

Conclusion:

Our data suggest that preoperative imaging features of ITSB and tumor size can predict pT3a RCC, which could impact patient counseling and surgical management. ITSB also significantly correlated with recurrence and thus appears to be a strong prognostic indicator. Further studies and independent validation will be required.

Funding: N/A