Clinical characteristics and outcomes of IgD myeloma: experience across UK national trials.

Immunoglobulin D (IgD) myeloma is a subtype often considered to have adverse features and inferior survival, but there is a paucity of data from large clinical studies. We compare the clinical characteristics and outcomes of patients with IgD myeloma from UK phase 3 myeloma trials analyzed in 2 groups: old (1980-2002) and recent (2002-2016) clinical trials, based on the time of adoption of novel myeloma therapies. Patients with IgD myeloma comprised 44 of 2789 (1.6%) and 70 of 5773 (1.2%) of the old and recent trials, respectively. Overall, IgD myeloma was associated with male predominance, low-level paraproteinemia (<10g/L), and λ light chain preference. The frequency of ultra-high-risk cytogenetics was similar in IgD myeloma compared with other subtypes (4.3% vs 5.3%, P > .99). Despite the old trial series being a younger group (median age: 59 vs 63 years, P = .015), there was a higher frequency of bone lesions, advanced stage at diagnosis, worse performance status, and severe renal impairment compared with the recent trials. Furthermore, the early mortality rate was significantly higher for the old trial series (20% vs 4%, P = .01). The overall response rate following induction therapy was significantly higher in the recent trials (89% vs 43%, P < .0001), and this was consistent with improved median overall survival (48 months; 95% confidence interval [CI] 35-67 months vs 22 months; 95% CI, 16-29 months). Survival outcomes for IgD myeloma have significantly improved and are now comparable to other myeloma types because of earlier diagnosis, novel therapies, and improved supportive care. This trial was registered at clinicaltrials.gov as # NCT01554852.
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