Growth kinetics of venous tumor thrombus in patients with renal cell carcinoma

INTRODUCTION: Some patients with renal cell carcinoma (RCC) present with venous tumor thrombus (VTT). The extent of the VTT is related to survival, so prompt surgical care is recommended. However, studies evaluating the natural history of VTT in patients with RCC are rare. We sought to evaluate the growth kinetics of VTT in patients with RCC using preoperative cross-sectional images. MATERIALS AND METHODS: We identified patients who underwent radical nephrectomy and venous tumor thrombectomy at our institution from 01/2009 to 02/2022. We included those with a minimum of 2 adequate preoperative imaging studies (contrast-enhanced Computerized Tomography (CT), noncontrast Magnetic resonance imaging (MRI), or contrast-enhanced MRI), at least 14 days apart. We measured VTT in each study to calculate growth rate, and evaluated predictors of faster growth (demographics, histology, laterality, tumor diameter, and staging). To assess the relation between clinical variables and VTT growth, we used the Wilcoxon Rank-Sum, Kruskal–Wallis, and Spearman correlation tests. RESULTS: A total of 30 patients were included in the analysis. The median time interval between studies was 33 days. Patients were mostly Caucasian and Males (90% and 70%, respectively). Most patients underwent a CT scan as their initial imaging study (66%), followed with an MRI as second study (73%). The mean venous tumor thrombus growth rate was 0.3 mm/d (standard deviation of 0.5mm), and only rhabdoid/sarcomatoid differentiation showed an association with tumor thrombus growth rate (0.3 vs. 0.63 mm/d, P = 0.038). CONCLUSIONS: To the best of our knowledge, this is the first study evaluating the natural growth rate of venous tumor thrombus in patients with renal cell carcinoma. We found that tumor thrombi grew an average of 0.3 mm/d (1.0 cm/month) and that those with sarcomatoid and/or rhabdoid differentiation grew faster (0.63 mm/d). Further studies are needed to validate these results and provide a better understanding of tumor thrombus kinetics.