Renal Sinus Fat Invasion in pT3a Clear Cell Renal Cell Carcinoma Affects Outcomes of Patients Without Nodal Involvement or Distant Metastases

Purpose: According to the 2002 American Joint Committee on Cancer TNM classification, perinephric and renal sinus fat invasion are classified as pT3a renal cell carcinoma. However, only a few studies have assessed the impact of sinus fat invasion on patient survival and with controversial results. We analyzed the impact of sinus fat invasion on cancer specific survival in a cohort of patients with pT3a clear cell renal cell carcinoma. Materials and Methods: We retrospectively analyzed data on 115 consecutive patients treated with open radical nephrectomy for unilateral, sporadic pT3a clear cell renal cell carcinoma at our department from 1989 to 2006. All pathological specimens were rereviewed by a single uropathologist. The prognostic role of sinus fat invasion in cancer specific survival was assessed by Cox proportional hazards regression models. Results: Ten patients had direct ipsilateral adrenal invasion and were excluded from analysis. A total of 105 patients with clear cell renal cell carcinoma were evaluated. Median followup was 38 months. In the overall population sinus fat invasion did not reach independent predictive status in terms of cancer specific survival on multivariate Cox regression analysis after adjusting for age, performance status, tumor dimension, tumor grade, synchronous metastases, nodal involvement, sarcomatoid differentiation and coagulative necrosis. In the subset of patients with pNx/pN0 M0 (83) the actuarial 5-year cancer specific survival was 71.9% and 45.5% for those with perinephric fat invasion only and sinus fat invasion, respectively (p = 0.025). Sinus fat invasion achieved an independent predictive role on multivariable Cox regression analysis (p = 0.048, HR 2.06). Conclusions: Sinus fat invasion in clear cell renal cell carcinoma significantly affects cancer specific survival in patients without nodal or distant metastases. However, sinus fat invasion is not associated with worse cancer specific survival in cases of metastatic disease.