Detection of the MYD88^L265P and CXCR4^S338X mutations by cell-free DNA in Waldenström macroglobulinemia

We aimed to detect the MYD88^L265P and CXCR4^S338X mutations in cell-free DNA (cfDNA) in patients with Waldenström macroglobulinemia (WM). We collected peripheral blood and paired bone marrow aspirates from 27 WM patients (including 16 patients with newly diagnosed WM, 3 patients with WM in relapse and 8 patients with WM during treatment). cfDNA was extracted from peripheral blood using a QIAamp Circulating Nucleic Acid Kit. The MYD88^L265P and CXCR4^S338X mutations were detected by real-time allele-specific PCR (AS-PCR) in cfDNA and genomic DNA (gDNA) extracted from bone marrow aspirates. The sensitivity of real-time AS-PCR for detecting MYD88^L265P in cfDNA was determined using a serial dilution of 10%, 2%, 0.4% and 0.08% MYD88^L265P cfDNA in wild-type cfDNA. Among the 27 patients, MYD88^L265P was detected in 88.9% of them in gDNA and in 85.2% of them in cfDNA, with a concordance rate of 96.3%. The concordance rates were 93.8%, 100% and 100% in patients with newly diagnosed WM, patients with WM in relapse and patients with WM during treatment, respectively. The sensitivity of real-time AS-PCR for detecting MYD88^L265P in cfDNA was 0.4%. CXCR4^S338X was detected in 6.3% of the 16 newly diagnosed WM patients in both gDNA and cfDNA, with a concordance rate of 100.0%. It is feasible to apply cfDNA to detect MYD88^L265P and CXCR4^S338X in WM patients with a high concordance rate.