The extent of tumour fat invasion affects survival in patients with renal cell carcinoma and venous tumour thrombosis

OBJECTIVE To investigate the effect of presence and extent of tumour fat invasion (TFI) - perinephric invasion (PFI), renal sinus fat invasion (RSFI) or both PFI and RSFI - on cancer-specific mortality (CSM) in patients with renal cell carcinoma (RCC) and venous tumour thrombus (VTT). METHODS We examined 184 consecutive patients with RCC with VTT treated with nephrectomy between 1987 and 2007. Associations with CSM were evaluated by univariable and multivariable Cox proportional hazard models. RESULTS Median follow up was 21 months. The 5-year CSM-free survival estimates were 75%, 36% and 20% in patients with VTT without TFI, those with VTT with PFI or RSFI, and those with VTT with both PFI and RSFI, respectively (P <0.001). In multivariable analyses, presence of either PFI or RSFI was associated with a two-fold increased risk of CSM, whereas presence of both PFI and RSFI was associated with a three-fold increased risk of CSM, relative to VTT-only cases. The inclusion of the variable describing the presence and extent of TFI in a base model including pT stage, Fuhrman grade and presence of nodal disease and metastatic disease significantly increased the accuracy in predicting CSM (+2.1%; P <0.001) in patients with VTT. CONCLUSIONS Patients affected by RCC with VTT and TFI have a higher risk of CSM relative to cases with VTT only. Patients with both PFI and RSFI showed increased CSM compared with patients with either PFI or RSFI. Our results suggest TFI should be accurately evaluated and included in routine pathological reports to provide better patient risk stratification.