Waldenstrom's macroglobulinemia: population based studies of familial aggregation and prognostic factors

Background Waldenstrom’s macroglobulinemia (WM) is a rare lymphoproliferative disorder with a world-wide incidence of 3-4 patients per million persons per year. In Sweden, the incidence was about three times higher, and approximately 100 patients per year are reported to the Swedish Lymphoma Registry (SLR). Our aim was to study the WM population with focus on incidence and survival in relation to clinical prognostic factors and primary therapies (Paper I-II). We also discussed the diagnostic difficulties in patients with non-WM lymphoplasmacytic lymphoma (LPL). In Paper III-IV, we study familial WM from different aspects to better understand underlying pathogenetic factors. Patients and methods The patients in all four studies were collected from SLR. In papers I and II, a total of 1511 patients with WM and non-WM LPL were registered between 2000 and 2014, and medical records were retrieved for 1139 patients (75%). A retrospective review showed that 981 and 33 (after review by haematopathologist) of these patients fulfilled the World Health Organization (WHO) diagnostic criteria for WM and non-WM LPL, respectively. In Paper III and IV, we used SLR and the Northern Lymphoma Registry (NLR) for the years 1997- 2011. We identified 12 families with a family history of WM, IgM monoclonal gammopathy of undetermined significance (MGUS) and/or multiple myeloma (MM). Results In paper I, the overall survival (OS) for WM improved between the two time periods, 2000-2006 and 2007-2014, with a five-year OS of 61% and 70%, respectively. Significant prognostic factors for OS at the time of diagnosis in asymptomatic patients in no need of therapy were age, poor performance status (PS), haemoglobin ≤115 g/l, and female sex. Elevated lactate dehydrogenase (LDH) level and haemoglobin ≤115 g/l were significant prognostic factors for patients receiving therapy 0-3 months after diagnosis. The level of the IgM monoclonal immunoglobulin (MI) had no significant prognostic value. Rituximab included in first-line therapy was associated with improved survival. Paper II describes the differential diagnostic difficulties in non-WM LPL, especially with Marginal Zone Lymphoma (MZL). The non-WM LPL patients had more adverse prognostic factors as elevated LDH, anaemia, and lymphocytosis at diagnosis compared to the patients with WM. Despite this, the OS did not significantly differ between the groups (P = 0.249). The median OS for non-WM LPL was 71 months and the three-year and five-year sur