The use of medical claims to assess incidence, diagnostic procedures and initial treatment of myelodysplastic syndromes and chronic myelomonocytic leukemia in the Netherlands.

Myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML) may be underreported in cancer registries such as the Netherlands Cancer Registry (NCR). Analysis of Dutch medical claims can complement NCR data on MDS and CMML. We analyzed data on 3681 MDS patients and 235 CMML patients aged ≥18 years with initial claims for MDS or CMML from the Dutch nationwide medical claims-based Diagnosis Treatment Combination Information System (DIS) between 2008 and 2010. Clinical information was available in the DIS. MDS and CMML were diagnosed without a bone marrow (BM) examination in almost half of the patients. The age-standardized incidence rate (ASR) per 100,000 in the cohort that underwent BM examinations compared with NCR data was 2.8 vs. 3.3 for MDS and 0.2 vs. 0.4 for CMML in 2008-2010. A conservative treatment approach was associated with increasing age and absence of BM examination in MDS (p<0.001 for both) and CMML patients (p<0.033 for both). In conclusion, the ASR of MDS in the cohort that underwent BM examinations was comparable with the NCR. The majority of elderly patients, either with or without BM examinations, received no therapy. Together, MDS and CMML may be misdiagnosed and inappropriately managed without a BM confirmation.