The incidence of MDS in Canada is not known. Diagnosis of MDS is often challenging as dysplastic features on bone marrow may be non-specific, requiring exclusion of other disorders. The province of Manitoba, with a population of 1.2 million, has a cancer registry which has included patients with MDS since 2001. In this province, hematology diagnostic services are centralized at two teaching hospitals and the few bone marrows performed outside are reviewed centrally. This provided us with the opportunity to use registry data and bone marrow records to determine the incidence of MDS. We hypothesized that for an accurate estimate, a proportion of MDS cases would require follow-up data.
Retrospective study to examine all cases of MDS, which included chronic myelomonocytic leukemia (CMML) diagnosed in Manitoba. All adult Manitobans diagnosed with MDS and CMML (excluding RAEB-T), from 01/2006 to 12/2007 were identified from the cancer registry using ICD-O-3 topography code C42.1 and morphology codes 9980/3, 9982/3, 9983/3, 9985/3, 9986/3, 9987/3, 9989/3 and 9945/3. Bone marrow records for the same period were reviewed to identify all cases that had features of MDS. The clinical charts of all these patients were reviewed centrally to exclude those whose clinical course or repeat investigations suggested an alternative diagnosis.
A total of 80 patients with newly diagnosed MDS were identified. The age adjusted incidence of MDS was 3.26/100,000. Incidence was higher in men (4.05/100,000) as against women (2.57/100,000). Incidence varied significantly with age at diagnosis: <49yr: 0.12; 50–59yr: 2.24; 60–69yr: 10.63; 70–79yr: 20.41 and >80yr: 21.93. Eleven cases (13.75%) were not known to the cancer registry but were detected on reviewing the bone marrow data. From the registry, nine cases (11.25%) were excluded as the chart review and follow-up revealed alternative diagnoses.
The incidence of MDS for Manitoba is similar to published rates in Europe and the USA. This may be an underestimation of the actual incidence, as elderly patients may not undergo bone marrow examination if the therapeutic intervention is only supportive. Cancer registries that include MDS based on one-time bone marrow reports should include a review process of confirming or excluding the diagnosis of MDS based on follow up investigations and course of illness.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.