Leukemia as a cause of death among patients with myelodysplastic syndromes (MDS) in a population- based cancer registry: improving estimates of MDS-related mortality in the population.

Myelodysplastic syndromes (MDS), a heterogeneous group of myeloid neoplasms diagnosed mostly in elderly persons, are of increasing interest in an aging population and are associated with variable risk of progression to acute myeloid leukemia (AML). The numbers of deaths related to MDS in the population are underestimated in routine US cancer mortality statistics which are based on only the underlying cause (UC) rather than multiple causes (MCs) of death recorded on death certificates. Additional MDS-related deaths, however, may be missed if some MDS patients die with mention of leukemia but not MDS on their death certificate. This requires studies of MCs of death among all MDS patients in population-based tumor registries. This study examined MCs of death among patients diagnosed with MDS in 2001- 2009 and reported to the population-based Connecticut Tumor Registry. MDS was the UC for 199 deaths (25.7% of all 773) and was coded as other than UC for 160 (20.7%). Another 121 (15.7%) death records, however, had leukemia without mention of MDS; the majority were coded to AML and most of the others as unspecified type of acute leukemia. If these 121 deaths are added to the 359 with mention of MDS, the total of MDS-related deaths would be 480 (or 62.1% of all 773 deaths). A total of 178 deaths (23.0% of all 773) were coded to leukemia as the UC, and would be included with leukemia (not MDS) in routine cancer mortality statistics. Leukemia diagnosed since 2010 in MDS patients is reportable to registries as a new primary cancer. This new rule will help central cancer registries to confirm leukemia diagnoses coded on death records, as part of the process of improving surveillance of cancer mortality rates in the population.