Characterizing Tumor Thrombus Arising from Non–Clear Cell Renal Cell Carcinoma

Background: Renal cell carcinoma (RCC) can exhibit a unique vascular tropism that enables tumor thrombus extension into the inferior vena cava (IVC). While most RCC subtypes that form tumor thrombi are of clear cell (cc) histology, non–clear cell (ncc) subtypes can also exhibit this unique growth pattern. Objective: To characterize clinicopathologic differences and survival outcomes among patients with IVC tumor thrombus arising from ccRCC versus nccRCC. Design, setting, and participants: Patients diagnosed with IVC tumor thrombus secondary to RCC in our institutional experience from 2003 to 2021 were identified. Outcome measurements and statistical analysis: Clinicopathologic characteristics were compared by histology. Perioperative and oncologic outcomes including recurrence-free (RFS), overall (OS), and cancer-specific (CSS) survival were assessed using multivariable Cox regression analyses. Results and limitations: The analyzed cohort included 103 patients (82 ccRCC and 21 nccRCC). There were no significant differences in baseline demographic parameters. Patients with nccRCC were more likely to have regional lymph node involvement (42.9% vs 20.7%, p = 0.037). No differences in perioperative outcomes, IVC resection, or IVC reconstruction were observed between groups. The median follow-up time was 30 mo. The median RFS was 30 (nccRCC) versus 53 (ccRCC) mo (p = 0.1). There was no significant difference in OS or CSS. This study was limited by its small sample size. Conclusions: Patients with IVC tumor thrombus arising from ccRCC and nccRCC exhibit similar perioperative and oncologic outcomes. While surgical appropriateness was not impacted by histologic subtype, multimodal strategies are needed to improve outcomes for patients with tumor thrombus. Patient summary: Renal cell carcinoma (RCC) can uniquely invade vasculature and form a tumor thrombus. This study examined the difference in outcomes of patients with tumor thrombus based on RCC subtype (clear cell vs non–clear cell). We found that patients exhibited similar surgical and survival outcomes regardless of RCC type.