IgD myeloma: A unique subtype with unclear prognostic significance.

Abstract

Aim: IgD myeloma is a rare plasma cell dyscrasia which is traditionally reported to have a poor outcome compared to patients with other types of M protein. This is thought to be due to higher rates of renal failure, chemotherapy resistance and a more aggressive clinical course. Recent studies have reported conflicting evidence into the survival outcomes of patients with IgD myeloma (Wang GR, Sun WJ et al. 2016, Chen L, Fan F et al. 2019). We therefore aimed to analyse the presentation and prognosis of IgD myeloma in a local cohort of patients in the era of novel therapies. Method(s): Eight patients with an IgD M protein were identified from Monash Medical Centre, Victoria, based on serum electrophoresis records in patients between 2013 and 2018. Retrospective data were collected in regards to M-protein type and size, biochemical and bone marrow analysis at presentation, renal function, co-morbidities and treatment received. Result(s): Median age at diagnosis was 75.5 years of age (range 51-83 years old). 50% presented with anaemia and 75% presented with renal failure with one patient requiring dialysis. The majority had high serum-free light chains at diagnosis with 87.5% having affected light chain above 1000 mg/l. All patients had ISS stage 3, 62.5% had R-ISS stage 3 disease at diagnosis. A single patient had smouldering myeloma without a myeloma defining event after 24 months of observation. Of the remaining patients, 85% received bortezomibbased induction, and 15% received thalidomide-based induction. Only one patient proceeded to autologous transplant. Overall survival in IgD myeloma patients was not statistically different from non-IgD myeloma patients (median 40 vs. 53 months; P = 0.332). Conclusion(s): IgD myeloma remains a rare plasma cell dyscrasia and presents commonly with high serum-free light chains, renal disease and anaemia. In our cohort, survival did not appear worse than non-IgD myeloma patients.