Preoperative β2 Microglobulin Is a Prognostic Factor in Patients with Renal Cell Carcinoma and Normal Kidney Function

β2 microglobulin is a non-glycosylated 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.

Using the Emory kidney cancer database, patients with any stage or histology RCC who underwent partial or radical nephrectomy from 2014 to 2022 and had an available β2 microglobulin within 90 days before surgery were included. Following manufacturer's recommendation, 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 and cancer-specific survival. Subgroup analysis was performed between patients with and without renal dysfunction (defined as an estimated glomerular filtration rate (eGFR) of ≤ or > 60 mL/min/1.73m²) and with and without metastatic disease.

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, elevations in β2 microglobulin levels remained significantly associated with OS and CSS in patients with normal renal function and non-metastatic disease.

Preoperatively elevated β2 microglobulin levels are 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.