Determination of MYD88 and CXCR4 Mutations for Clinical Detection and Their Significance in Waldenström Macroglobulinemia

Abstract Purpose: This study aims to explore the incidence and clinical features of MYD88 and CXCR4 mutations in patients with Waldenström macroglobulinemia (WM) and determine the optimal method for routine clinical practice. Additionally, we seek to evaluate the prognostic significance of these features across various therapeutic backgrounds [the cytotoxic group, the rituximab/bortezomib-based group, and the Bruton tyrosine kinase inhibitor (BTKi) group]. Experimental Design: A total of 385 symptomatic patients with WM were analyzed for MYD88 and CXCR4 mutations using Sanger sequencing, next-generation sequencing, allele-specific qPCR (AS-PCR), and/or droplet digital PCR (ddPCR). Results: The overall MYD88 mutation rate was 87.8%, relatively lower than that in the Western cohort. Both AS-PCR and ddPCR demonstrated high sensitivity in unsorted samples, detecting 98.5% and 97.7% of mutations, respectively, including those with low tumor burdens. The total CXCR4 mutation rate was 30.9%, with next-generation sequencing exhibiting the highest sensitivity of 78.0%. CXCR4 mutation was significantly linked to shorter OS only within the BTKi treatment group. The multivariate analysis indicated that MYD88 and CXCR4 mutations were not independent prognostic factors in the non-BTKi group when considering the International Prognostic Scoring System for Waldenström macroglobulinemia (IPSSWM) clinical staging. However, in the BTKi treatment group, these mutations emerged as independent adverse prognostic factors, overshadowing the prognostic significance of the IPSSWM classification (MYD88: HR, 0.229; P = 0.030; CXCR4: HR, 3.349; P = 0.012). Conclusions: Testing for MYD88 mutations using AS-PCR or ddPCR in unsorted samples is viable for routine clinical practice. Under BTKi treatment, MYD88 and CXCR4 mutations hold greater prognostic importance than IPSSWM staging in WM.