Waldenström Macroglobulinemia (WM) is defined by a bone marrow lymphoplasmacytic infiltration and the presence of a monoclonal immunoglobulin M (IgM) in blood. This chronic lymphoproliferative disorder requires treatment only in case of symptoms, according to accurate criteria described during the second Workshop on WM i.e. in case of cytopenia, bulky organomegaly, immunological or physicochemical consequences of the presence of IgM in circulating blood. A MYD88 mutation, typically a MYD88(L265P), is found in 90% of WM patients. Other gene abnormalities have been observed, the most frequent is a mutation in the CXCR4 gene. Overall, gene mutations in WM involve only a limited number of signalling pathways, yielding the activation of NFkB, namely : the TLR and MYD88 pathway (with an activation of NFkB and BTK in case of MYD88(L265P) mutation), the BCR pathway (involving btk and associated with activations of both NFkB, and erk akt pathway) and the CXCR4 pathway (CXCR4 is a receptor of CXCL12, it is also associated with activations of ERK/MAPK and PI3K). Abnormalities of some of genes, such as TP53, of the expression of the protein CXCL13 and genes involved in the interleukin 6 secretion have been associated with some clinical characteristics.

The purpose of this project is to define the prognostic role of the detection of circulating tumoral DNA (ctDNA) at the end of treatment for the progression/relapse risk within the first 3 years after the first 6 months of treatment.

Inclusion Criteria:

• Patient with WM according to diagnostic criteria
• Patients with WM followed in one of the centre of North-Western region.
• Patients requiring first-line or subsequent-line therapy
• Patients agreement for giving informed consent.
• Social insurance system affiliation

Exclusion Criteria:

• Patients with another chronic B-cell malignancy
• patients with other lymphoplasmacytic proliferations
• patients with marginal zone lymphoma.
• Patients with WM and histologic transformation
• Absence of informed consent