Reduced prognostic value of beta-2-microglobulin for time to first treatment in CLL patients with compromised kidney function

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults and characterized by a highly heterogeneous clinical course. The CLL-IPI and the OCLL-1 scores are among the best validated tools to predict time-to-first-treatment. In both models, elevated beta-2-microglobulin plasma level (B2M) is an independent prognostic factor. Yet, B2M is commonly increased in patients with chronic kidney disease (CKD) <i>per se</i> and both models were not adjusted for CKD. We analyzed the clinical outcomes of 297 treatment-naive CLL patients between 2000 and 2022. B2M was more frequently elevated in CKD patients and lost prognostic significance at the threshold > 2.5 mg/L. Both CLL-IPI and OCLL-1 failed to facilitate prognostic segregation in CKD patients. 22.2% of CKD patients were assigned to a higher CLL-IPI risk group due to elevated B2M. Our results suggest that both models overestimate the risk for disease progression and need to be interpreted with caution in CKD patients.