The prognostic utility of preoperative β2 microglobulin in patients with renal cell carcinoma.

565 Background: β2 microglobulin is a nonglycosylated protein synthesized by all nucleated cells. It has been utilized as a tumor marker in several different malignancies, however, studies examining its role in renal cell carcinoma (RCC) are limited. Methods: Using the Emory kidney cancer database, patients with any stage or histology RCC who underwent partial or radical nephrectomy from 2000 to 2022 and had an available β2 microglobulin within 90 days before surgery were included. β2 microglobulin ≥ 2.34 mg/L was considered elevated. Patient and surgical characteristics were recorded. Kaplan-Meier curves and multivariable Cox hazards models were used to assess the association between an elevated β2 microglobulin and overall (OS) and cancer-specific survival (CSS). Subgroup analysis was performed based on renal function (estimated glomerular filtration rate (eGFR) ≤ or > 60 mL/min/1.73m 2 ) and metastatic disease status. Results: Of 429 patients who met inclusion criteria, 178 (41.5%) had an elevated preoperative β2 microglobulin. After adjusting for confounders, an elevated β2 microglobulin was independently associated with worse CSS (HR 2.08 [95% CI 1.20–3.60]; p = 0.009) and OS (HR 1.58 [95% CI 1.03–2.41]; p = 0.035) compared to a normal β2 microglobulin. On subgroup analysis, however, elevated β2 microglobulin remained significantly associated with worse OS/CSS only in patients with normal renal function and non-metastatic disease (Table). Conclusions: A preoperatively elevated β2 microglobulin level is independently associated with worse OS and CSS in patients with RCC undergoing nephrectomy. The utility of β2 microglobulin as a prognostic indicator is most relevant for patients with normal renal function and non-metastatic disease. Multivariable Cox hazards model for the effect of preoperative β2 microglobulin on cancer-specific and overall survival in patients with renal cell carcinoma according to renal function and metastatic disease status. Covariants n(%) Cancer-specific SurvivalHazard Ratio (95% CI) p-value Overall SurvivalHazard Ratio (95% CI) p-value β2 microglobulin ≥ 2.34 mg/L metastatic disease 102 (63) 0.95 (0.51-1.76) 0.872 0.93 (0.56-1.55) 0.779 non-metastatic disease 76 (28.5) 4.55 (1.24-16.77) 0.023 2.99 (1.37-6.54) 0.006 eGFR ≤ 60* 99 (23.1) 1.31 (0.69-2.49) 0.410 1.51 (0.95-2.41) 0.083 eGFR > 60* 79 (18.4) 2.90 (1.54-5.44) < 0.001 2.00 (1.19-3.36) 0.009 β2 microglobulin < 2.34 mg/L eGFR ≤ 60* 50 (11.7) 1.24 (0.55-2.78) 0.600 1.39 (0.74-2.60) 0.309 eGFR > 60* 201 (46.9) Ref Ref *Calculated using Chronic Kidney Disease Epidemiology Collaboration 2021 equation. Variables in model include age, sex, race, Body Mass Index (BMI), Charlson Comorbidity Index (CCI) pT stage, Fuhrman grade, presence of IVC thrombus, receipt of systemic therapy, and IMDC risk score (metastatic patients only).