The Epidemiology of MDS and Myeloproliferative Disorders
Abstract & Commentary
By Andrew Artz, MD, Division of Hematology/Oncology, University of Chicago, Chicago, IL. Dr. Artz reports no financial relationship to this field of study.
Synopsis: Epidemiologic data have recently become available in the U.S. for myelodysplastic syndromes (MDS), chronic myeloproliferative disorders (CMD) and chronic myelomonocytic leukemia (CMML) after registries began including these conditions in 2001. The incidence rates per 100,000 were 3.3 and 2.1 for MDS and CMD respectively and were highest among whites. Survival at 3 years was 45% for MDS and 80% for CMD. These descriptive data for uncommon conditions may be a useful reference for practicing oncologists.
Source: Rollison D, et al. Epidemiology of myelodysplastic syndromes and chronic myeloproliferative disorders in the United States, 2001-2004, using data from the NAACR and SEER programs. Blood. 2008;112:45-52.
Myelodysplastic syndromes (MDS) and chronic myeloproliferative disorders (CMD) encompass a heterogeneous group of clonal hematopoietic disorders. Epidemiologic data in the United States (U.S.) have been limited as these conditions were only included in the cancer registries in the U.S. starting in 2001. Based upon data from the Surveillance, Epidemiology, and End Results (SEER) Program that covers 26% of the U.S. population, the increasing frequency of MDS with advancing age and among men was demonstrated.1 This study extends those findings by including both MDS and CMD as well as widening the population assessed by incorporating data from the North American Association of Cancer Registries (NAACCR). This provides the most complete picture of MDS and CMD epidemiology in the United States.
Cases of MDS, CMD and chronic myelomonocytic leukemia (CMML) from 2001 to 2003 were obtained from the NAACCR, a registry where data are reported from both the SEER program and the National Program of Cancer Registries. Survival data were based only on the SEER program. Diagnoses were based upon the ICD codes for the respective diseases but excluded BCR/ABL positive chronic myeloid leukemia. Most subtypes of MDS (eg, refractory anemia, refractory anemia with excess blasts) and CMD (eg, hypereosinophilic syndrome, polycythemia vera, essential thrombosis, chronic idiopathic myelofibrosis) are thus covered under these broad diagnostic categories.
The analysis revealed 24,798 patients were diagnosed with MDS overall whereas 16,119 were diagnosed with CMD. The rate of diagnoses not confirmed by histology (eg, bone marrow evaluation) or positive laboratory tests were only 4-5%. The average annual age adjusted incidence rates was 3.27 per 100,000 for MDS and 2.12 per 100,000 for CMD. The incidence of MDS had a striking association with older age; the incidence rate rose per 100,000 from 0.17 for those under 40 years of age to 36.4 for those 80 years and over. CMD increased as well with older age, albeit to a lesser extent than MDS. Both MDS and CMD were more frequent among whites. Refractory anemia (RA) was the most common subtype of MDS but almost 50% were classified as "not otherwise specified." CMML, often considered a type of MDS, was one-tenth as common as a diagnosis of MDS. For CMD, polycythemia vera was the most frequent subtype followed by essential thrombocytosis. The 3 year overall survival was 45% for MDS, 21% for CMML and 80% for CMD. Not surprisingly, older age adversely impacted survival for MDS and CMD as did white race.
Commentary
Epidemiologic information for myelodysplastic syndromes (MDS), chronic myeloproliferative disease and chronic myelomonocytic leukemia (CMML) has only recently become available in the United States after inclusion of these conditions in the cancer registries since 2001. The authors report valuable baseline data and show that such conditions are more common among whites and older adults. As with any epidemiologic study, the major limitations relate to accuracy of diagnosis and ascertainment of cases. Most of the cases were confirmed histologically or by laboratory test but certainly some cases may have been misclassified. Missed cases remain the largest problem. It is quite likely that many patients having abnormal hematologic values such as anemia or leukocytosis are never referred to an oncologist to render a definitive diagnosis. Physicians offices reported only 5% of cases further emphasizing that cases may be missed as non-oncologists are less likely to order definitive tests (eg, bone marrow evaluation) that would be reported by a hospital. Thus, the actual incidence rate may be considerably higher and that could also account in part for a greater number of cases among whites if whites were referred more frequently. Overall, MDS and CMML had relatively poor survival. The better survival in CMD was attributable to the two most common conditions of polycythemia vera and essential thrombocytosis.
The lack of a direct impact on treatment decisions often hinders interest in such studies and promotion by pharmaceutical companies. Even the authors offer no suggestion as to how to routinely apply such data. Nevertheless, this study can serve to illustrate the practical application of epidemiologic data. Awareness of risk factors for disease facilitates diagnostic decision making. For example, MDS is more common in white older men. For older anemic adults without a known cause, this prompts a greater pre-test probability of MDS. Also, the high rate of MDS considered "not otherwise specified" was the most frequent subtype reported whereas in MDS centers, almost all cases can be further classified (eg, refractory anemia with excess blasts). Because of a growing arsenal of treatments based in part on marrow subclassification, central review of pathology for cases not further classified should be entertained. Similarly, CMD not further classified could risk missing a condition such as hypereosinophilic syndrome in which some cases are exquisitely sensitive to imatinib. Finding accurate prognostic information to relay to patients can often be quite challenging. Survival results derived from the registry represent real world data rather than from clinical trial that are generally restricted to treatment protocol eligible patients. Registry data provide an excellent starting point although further individualization based upon prognostic factors is often required.
References
1. Ma X, et al. Myelodysplastic syndromes: incidence and survival in the United States. Cancer. 2007;109:1536-1542.
Epidemiologic data have recently become available in the U.S. for myelodysplastic syndromes (MDS), chronic myeloproliferative disorders (CMD) and chronic myelomonocytic leukemia (CMML) after registries began including these conditions in 2001.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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