IgD myeloma: clinical characteristics and a new staging system based on analysis of Japanese patients

The aim of this review was to compare the clinical characteristics and prognostic factors of Japanese and Western IgD myeloma patients, and also to introduce our new staging system, based on the analysis of Japanese patients. We reviewed 165 Japanese with IgD myeloma reported since the first Japanese case report in 1967 and compared these patients with Western IgD myeloma patients reported in the literature. Parameters evaluated were recorded at diagnosis. The staging systems of Durie and Salmon and the British Medical Research Council (BMRC) were also applied to our series. Survival curves were calculated according to the method of Kaplan & Meier and generalized Wilcoxon test and log-rank test were used to assess differences in survival. Multivariate analysis was performed by the Cox proportional hazard model. We were able to confirm the similarity of clinical features in Japanese patients and those reported in Western countries. We did, however, find small differences in the incidence of lymphadenopathy, thrombocytopenia, and high serum levels of creatinine, and in the 5-year survival rates. Assessment of prognostic factors influencing survival was compared in Japanese and Western patients. A multiple regression model in our series showed that light chain subtype and leukocyte count had a strong predictive relationship for duration of survival. A new risk grouping using these two major factors was introduced since neither the common staging system of Durie & Salmon nor those of the BMRC predicted survival in these patients; to date, there are still no reports from Western countries in this regard.