MYD88 L265P Variant Detection with Droplet Digital PCR in Waldenström Macroglobulinemia: Clinical Implications as a Tumor Burden and Prognostic Marker.

Waldenström macroglobulinemia (WM) is a B-cell lymphoproliferative disease characterized by IgM monoclonal gammopathy and bone marrow (BM) infiltration caused by lymphoplasmacytic lymphoma. The MYD88 L265P variant is present in >90% of WM cases. We used droplet digital PCR (ddPCR) to detect MYD88 L265P in initial BM samples from 15 patients with WM and assessed the implication of variant burden as a tumor load and prognostic marker. MYD88 L265P burden correlated with clinical indicators, including peripheral blood and BM lymphocyte percentages (P <0.001 and P =0.003, respectively), serum lactate dehydrogenase level (P =0.045), and platelet count (P =0.003). Patients classified into intermediate and high groups according to the Revised International Prognostic Score System for WM had higher MYD88 L265P copies/μL than patients in very low and low groups (P =0.017), as had patients with minor response or stable disease after primary treatment than those with complete, partial, or very good partial response (P =0.034). MYD88 L265P burden correlates well with multiple clinical indicators and has prognostic relevance, making it a potential marker for assessing tumor burden and predicting prognosis in WM.