[Kidney cancer stage pT3a: Fat invasion versus renal vein invasion.]

OBJECTIVE: We discuss the influence that involvement of fat (perirenal, sinus) and vascular structures (renal vein, segmental veins) have on cancer-specific mortality (CSM) rates in renal cancer.

METHODS: We conducted a retrospective analysis of 140 stage pT3a kidney tumors (114 clear cell, 9 type I papillary, 6 type II papillary, 11 chromophobe) surgically treated between 1997 and 2015. We conducted a cancer-specific survival study (Kaplan Meier) and a univariate and multivariate analysis of the variables: perirenal fat invasion, sinus fat invasion, renal vein invasion, segmental vein invasion and Fuhrman grade.

RESULTS: With a mean follow-up of 79 months, 47 deaths occurred overall (31.7%), 29 of which were due to the kidney tumor (CSM 20%). There were 50 cases of vascular invasion (35.7%), 40 cases with fat only invasion (28.6%) and 50 cases with invasion of both (35.7%). In the survival study, fat invasion had the least impact (17%), and invasion of both (fat and vascular structures) had the worst survival (48% of total mortality). Vascular invasion represents 35% of the mortality rate. In the multivariate study, Fuhrman grade 3-4 (HR 10.7), renal vein invasion (HR 9.2) and concomitant vascular and fat invasion (HR 5.6) are the factors with the greatest impact.

CONCLUSIONS: Tumor fat invasion has a lower impact on the CSM of kidney cancer than vascular invasion.