65: Biomarkers associated with Inferior Vena Cava (IVC) Thrombus in Patients (pts) with metastatic Renal Cell Carcinoma (mRCC) undergoing Cytoreductive Nephrectomy and receiving Immune Checkpoint Inhibitors (ICI)-based regimen.

Background: Inferior Vena Cava (IVC) Thrombus is associated with poor outcomes in pts with mRCC. A better understanding of circulating biomarkers could pave the way to determining their utility in pts with mRCC having an IVC thrombus.

Methods: We conducted a retrospective analysis of pts with mRCC receiving ICIs and undergoing cytoreductive nephrectomy at UTSW. We examined several blood parameters and compared 2 groups of pts with and without IVC thrombus. The primary goal was to evaluate the mean difference of biomarkers between the two groups: IVC thrombus (+) vs IVC Thrombus (-) using the two-sample t-test; secondary endpoints included progression-free survival (PFS) and overall survival (OS).

Results: From April 2016 to October 2022, 53 pts with mRCC were included, median age 63 years (range 36-86), 77% were male, and median follow-up was 20 months. IVC thrombus was present in 49% (n=26) pts at time of diagnosis. At baseline, a significant difference was observed between the two groups. Hemoglobin (Hb) was lower in pts with vs without thrombus (11.1g/dL vs 12.8 g/dL, p=0.01). Absolute Lymphocyte Count (ALC) (1.3 vs 1.6, p=0.03) and Absolute Eosinophil Count (AEC) (0.15 vs 0.2, p=0.01) were lower in pts with IVC thrombus, while Neutrophil-to-Lymphocyte ratio (NLR) (3.8 vs 2.9, p=0.02) and Neutrophil-to-Eosinophil ratio (NER) (30.9 vs 21.2, p=0.01) were higher. PFS (HR 0.75, 95% CI 0.31-1.78, p=0.57) and OS (HR 0.88, 95% CI 0.29-2.65, p=0.88) were not different between cohorts.

Conclusions: Several biomarkers seem to be associated with IVC thrombus. Lower AEC and ALC for pts with IVC thrombus may indicate thrombus sequestration. Further studies are needed to understand etiologies of these biomarkers correlated with presence of IVC thrombus in pts with mRCC.