Highly sensitive MYD88L265Pmutation detection by droplet digital PCR in Waldenström Macroglobulinemia

We here describe a novel method for MYD88L265Pmutation detection and minimal residual disease monitoring in Waldenström Macroglobulinemia, by droplet digital PCR, in bone marrow and peripheral blood cells, as well as in circulating cell free DNA. Our method shows a sensitivity of 5.00E-05, by far superior to the widely used allele-specific polymerase chain reaction (1.00E-03). Overall, 291 unsorted samples from 148 patients (133 Waldenstrom 11 IgG-lymphoplasmacytic lymphoma and 4 IgM-monoclonal gammopathy of undetermined significance), 194 baseline and 97 follow-up, were analyzed. 122/128 (95.3%) bone marrow and 47/66 (71.2%) baseline peripheral blood samples scored positive for MYD88L265PMoreover, to investigate whether MYD88L265Pby droplet digital PCR could be used for minimal residual disease monitoring, mutation levels were compared with IGH-based minimal residual disease analysis in 10 patients, showing to be as informative as to the classical, standardized but not yet validated in Waldenström Macroglobulinemia, IGH-based minimal residual disease assay (r2=0.64). Finally, MYD88L265Pdetection performed by droplet digital PCR on plasmatic circulating tumor DNA from 60 patients showed a good correlation with bone marrow (bone marrow median mutational value 1.92E-02, plasmatic circulating tumor DNA value: 1.4E-02, peripheral blood value: 1.03E-03). This study indicates that droplet digital PCR MYD88L265Passay is a feasible and sensitive tool for mutational screening and minimal residual disease monitoring in Waldenström Macroglobulinemia. Both unsorted bone marrow and peripheral blood samples can be reliably tested, as well as circulating tumor DNA, that represents an attractive, less invasive alternative to bone marrow for MYD88L265Pdetection.