Ethnic Disparities in Waldenström's Macroglobulinaemia in the United Kingdom - Analysis from the Wmuk Rory Morrison Registry

Introduction: Waldenström's Macroglobulinaemia (WM) is a rare indolent B-cell lymphoma characterised by lymphoplasmacytic infiltrate with an IgM paraproteinaemia. Approximately 400 patients (pts) are diagnosed annually in the United Kingdom (UK). National and regional registries provide important insights on the epidemiology and clinical features of this distinct uncommon disorder. Previous authors from the United States have reported significant differences in age at diagnosis and overall survival (OS) in WM between ethnic groups from Surveillance, Epidemiology and End Results data [1]. We aimed to determine baseline demographics, symptoms and survival outcomes across different ethnic groups in the UK.

Methods: We retrospectively reviewed data from the WMUK Rory Morrison Registry, collating descriptive data of WM as well as non-IgM Lymphoplasmacytic lymphoma (LPL) cases from 20 centres across the UK, diagnosed between June 1978 and May 2021. Research ethics approval was obtained.

Results: 732 pts with documented ethnicity were included here. Ethnicity was categorised in accordance with the UK National Census. Those other than the White cohort (662/732; 90%) were collectively termed 'Ethnic Minorities' (EM) (70/732; 9%): 39/70 (56%) Asian (13 Indian, 6 Chinese, 4 Pakistani, 16 other); 19/70 (27%) Mixed (1 White & Black African, 1 White & Asian, 1 Arab, 16 other); 12/70 (17%) Black (6 Caribbean, 3 African, 3 other).

Baseline characteristics are displayed in table 1. EM presented at a significantly younger age compared to White cohort (60 vs 64 years, p=0.01) and had a significantly lower paraprotein at diagnosis (11 vs 18g/L, p=0.05). MYD88 L265P mutation tested in 250 pts (34%): positive in the majority 218/250 (87%) and notably less common in EM (p=0.09), most significantly in the Asian cohort compared to White (67% v 88%, p=0.01). The EM cohort had a smaller proportion of WM diagnoses compared to White cohort (77% vs 93%, p=0.02) with the Asian cohort accounting for the highest proportion of non-IgM LPL (15% vs 4%, p=0.002). Bone marrow trephine infiltration at diagnosis was lower in the EM cohort compared to the White cohort, although not statistically significant (25% vs 37%, respectively; p=0.10). IPSSWM scores were similar throughout.

Approximately half of both the White & EM cohorts were asymptomatic at diagnosis. The most common presenting symptoms in EM were anaemia-related (10/34; 29%), B symptoms (6/34; 18%) and fatigue (4/34; 12%). 6/18 (33%) of Asians presented with cryoglobulinaemia, amyloid, nephropathy or acquired von Willebrand's Disease.

Of EM, 51/70 (73%) had treatment, 35/51 (69%) within the first year from diagnosis with time to treatment 2 months (range 0-364). Time to next therapy was 14 months. Median lines of therapy were 2 (range 1-8). The most common indication for first line therapy was lymphoma-related (16/39; 41%) followed by paraprotein-related (peripheral neuropathy, hyperviscosity and autoimmune) (13/39; 33%). First line therapies included Bendamustine-Rituximab (BR; 8/49; 16%), Dexamethasone Rituximab Cyclophosphamide (DRC; 7/49; 14%) and R-CHOP (5/49; 10%) with smaller proportions receiving Rituximab monotherapy, Cladribine + Rituximab or Fludarabine + Cyclophosphamide + Rituximab (FCR) (3/49 (6.1% each). Two of 41 (5%) of EM had first treatment as a part of a clinical trial, compared to 16/156 (10%) of the White cohort (p=0.28). Response to first line therapy was similar between the White & EM cohorts (Table 1).

For EM, at a median follow up of 7 years, 17 died (1/17; 6% disease related). Median OS was not reached (Figure 1). Estimated 5-year and 10- year OS was 91% (95% CI 96-80%) and 75% (95% CI 85-60%), respectively.

Conclusions: This first report on ethnic disparities in WM and non-IgM LPL in the UK identified key differences in presentation of disease. Ethnic minorities present at a younger age, with a lower paraprotein. The Asian cohort had a greater proportion of non-IgM LPL cases and fewer MYD88 mutated cases. A small proportion of Ethnic Minorities have treatment on a clinical trial which may warrant further attention. Further analysis including associations with socioeconomic status, deprivation indices and comorbidities are ongoing.

• Ailawadhi, Sikander et al. "Outcome disparities among ethnic subgroups of Waldenström's macroglobulinemia: a population-based study." Oncology vol. 86,5-6 (2014): 253-62. doi:10.1159/000360992