Background: Myelodysplastic syndromes (MDS) are a diverse group of clonal hematopoietic stem cell malignancies that primarily affect the elderly. Although the incidence of MDS in western countries has been well investigated, little is known about the incidence in Asian populations.
Methods: To identify the incidence of MDS in Japan, we used population-based registry data from 1993 to 2008. The data represented 33.1% of the Japanese population. A total of 7995 patients were reported to the registry with newly diagnosed MDS during the study period.
Results: Median age at diagnosis was 76 years. Incidence sharply increased with age, particularly in those aged over 70 years. The most recent crude incidence rate of MDS was 3.8 (95% CI 3.6–4.1) cases per 100 000 for men and 2.4 (95% CI 2.2–2.6) cases per 100 000 for women in 2008. Age-adjusted incidences of MDS in 2008, standardized by the world standard population, were 1.6 and 0.8 cases per 100 000 for men and women, respectively, while incidences standardized by the 1985 Japanese population were 2.5 and 1.2 cases per 100 000 for men and women, respectively.
Conclusions: Our study reveals that some elderly patients suffer from MDS in Japan, but the incidence is lower than in Western countries. In current clinical practice, many elderly MDS patients are treated with supportive therapy based on an incomplete diagnosis, suggesting that the incidence estimated in this study might still be substantially underestimated. Accurate evaluation of the health impact of MDS requires evaluation of the mortality of the disease, continued surveillance, and improvement in the quality of cancer registry data.