Epidemiology of Mylofibrosis from Three Different French Area Covered By a Population-Based Registry

Introduction: Myelofibrosis (MF) is one of the myeloproliferative neoplasms BCR-ABL1-negative. It is a rare disease, difficult to diagnose particularly with changes of the diagnosis criteria in the last twenty years. It is also difficult to treat MF because of lack of specific dug and/or validated therapeutic scheme. Scarce epidemiological data were available on MF and we used databases from three specialized registries in France to evaluated incidence rate, survival and treatment strategy used in the general population.

Methods: Cases diagnosed with Myelofibrosis (ICD-O-3: 9961/3) in Gironde, Côte d'Or and Basse-Normandie covering 3 530 000 inhabitants, between 01/01/20014 and 12/31/2014 were registered. Data were collected from laboratories and clinical charts. The vital status was updated at 01/01/2017. Incidence, clinical characteristics, survival and treatment were studied using the STATA-V13 software.

Results: They were 288 cases, 68% being male with a median age of 73 y-o. 65% of the cases were died at 5 years. 12% of the cases occurred after a previous solid tumor and 5% were secondary to a previous hemopathy. 62% had comorbidities at diagnosis in which 50% were cardiac conditions. At diagnosis, 83% had a splenomegaly; blast and bone marrow cells were present in peripheral blood in respectively 30% and 73%. Jak2 V617F was found in 88%, CALR in 8% and MPL mutation in 4% of the cases. The most frequent karyotypic abnormality was the del 20q (20%). IPSS score was calculated in 34% of the cases and 20% of them had a low risk score. 75% of cases were treated: 60% had hydroxycarbamide, 29% had ruxolutinib phosphate and 10% had thalidomide. Hydroxycarbamide was used in 48% of the cases in Basse Normandie, 68% in Côte d'Or and 64% in Gironde (p=0.001). EPO was used in 48% of cases and corticoids in a quarter of them. The transformation rate into acute myeloid leukemia was 25% in Côte d'Or, 12% in Gironde and 9% in Basse-Normandie (p=0.01). The 5 years observed survival was 25% and the 5-years net survival was 36%, without difference between male and female. It was 66% in cases under 55 y-o and was 25% in patients older than 75 y-o (p<0.001). The age-standardized 5-years survival was 50% in Basse Normandie, 42% in Côte d'Or and 37% in Gironde (ns).

Conclusions: This study highlights biological and clinical characteristics of this rare disease in France. It also emphasizes some differences in the way of taking in charge these patients and in their survival rate. Even if it was not always statistically significant, patients from Basse Normandie appeared to receive less hydroxycarbazine, had a lower rate of AML transformation and had a slight better survival. This type of study should be extended to French cancer registries data for validation on a larger cohort and for guidance in patient management.