Incidence and outcome of chronic myeloproliferative disorders: A population-based study from a cancer registry in northern Italy

Background Because in the past Chronic Myeloproliferative Disorders (CMPD) were not considered to be malignant conditions, cancer registries rarely recorded data on these diseases. Thus, information on incidence and outcome of CMPD in the population is limited. The aim of the present study was to better define epidemiological data of CMPD by examining all cases identified by the Modena Cancer Registry (MCR). Materials and methods We considered all cases of CMPD diagnosed in the Province of Modena (population 633.993 at 2001 Census). Cases, except Chronic Myeloid Leukemia, diagnosed from 1997 to 2005, were identified using the MCR database and the archival files of the centralized hemolymphopathological laboratory at Modena Cancer Centre according to ICD-O-3 codes 9950, 9960-64. Death certificate, cytology and histology report, both local and national reports of hospital admission, ICD-9 code reported in medical records were used as sources for identifying new CMPD cases and their outcome. All cases were checked and validated by a hematologist (A.B.) and a pathologist (G.B.) by a review of the original pathology report. Uniform diagnostic criteria were adopted, because the large majority of bone marrow aspirate and biopsy were examined by the same pathologist (G.B.). Clinical and follow-up data were retrieved by active search of discharge letters, review of hospital records and interview of general practitioners. Information on vital status was achieved from official population registries. Age standardized rates (ASR) were calculated according to the World Standard population. The dates of diagnosis and death or the closing date of study (December 2006) were used to estimate survival. Observed survival and relative survival were calculated according to Kaplan-Meier method and the Hakulinen approach, respectively. Results According to the 2001 World Health Organization (WHO) classification, a total of 380 cases of CMPD were identified. There were 155 Essential Thrombocythemia (ET) (41% of all CMPD), 114 Policythemia Vera (PV) (30%), 75 Idiopathic Myelofibrosis (20%), 2 Hypereosinophilic Syndrome/Chronic Eosinophilic Leukaemia (0.5%), 1 Chronic Neutrophilic Leukemia (0.3%) and 31 CMPD not otherwise specified (8%). The ASR of CMPD was 3.2/100,000 varying slightly (from 2.5 to 4.1/100,000) during the study period (p = 0.11); the crude incidence rate was 6.6/100,000. Median age at diagnosis was 69 years. No statistically significant differences were observed between sex regarding incidence and age at diagnosis. Overall relative survival was 97%, 89% and 88% at 1, 3 and 5 years after diagnosis, respectively. Analyzing CMPD, we observed a better survival for ET and PV in comparison with other subtypes (p = 0.01). Conclusions To our knowledge, this study is the first in Italy providing information on the incidence and outcome of CMPD using population-based data. Our results confirm that the risk of developing CMPD increases with age. The incidence of CMPD was substantially stable during the study period. Overall survival patterns reflect the well known chronic course of these diseases. As expected, we observed important differences in overall survival by WHO subtypes. We believe that the availability of precise epidemiological data, in particular those regarding outcome could help clinicians in choosing the most appropriate cost-effective treatments.