OBJECTIVETo investigate the significance of serum IgD quantitation in evaluation of clinical efficacy in IgD myeloma.

METHODSSerum IgD and free light chain (sFLC) levels were determined by immune scatter turbidimetry with SPA plus analysis machine in 29 patients with IgD multiple myeloma (MM) achieving VGPR or better response following previous treatments. The concurrent immunofixation electrophoresis (IFE) results were also incorporated and analyzed.

RESULTSIncreased IgD levels were detected in 1 of 12 patients achieving sCR, 2 of 5 patients achieving CR and 4 of 12 patients achieving VGPR, respectively. The median progression-free survival (PFS) was 38.5 months, 34.1 months and 15.5 months for patients achieving sCR, CR and VGPR, respectively, with a significant difference between sCR and VGPR groups (P=0.022), and between CR and VGPR groups (P=0.018). There was no difference in overall survival (OS) among sCR, CR and VGPR groups (P>0.05). The median PFS were 7.8, 33.7 and 43.9 months, respectively for the patients with both abnormal sFLC ratios and IgD levels (6 cases, Group A), with either abnormal sFLC ratios or increased IgD levels (10 cases, Group B) or with normal sFLC ratios and IgD levels (13 cases, Group C). A significant PFS benefit of Group A over Group C was found (P=0.033), and no differences in terms of OS among three groups (P>0.05).

CONCLUSIONIgD levels may remain abnormal in IgD MM patients who have achieved VGPR or better response, and IgD quantitation represented a useful assay complementary to the current lab examinations. IgD quantitation assay was of significance in clinical efficacy evaluation and survival judgement, and should be incorporated into the evaluation parameters used for IgD MM in addition to sFLC and IFE assays.