Clinical, Pathologic Characteristics and Survival Of Adult Patients With Essential Thrombocythemia: Experience In a Reference Center In Mexico

Essential thrombocythemia (ET) is a myeloproliferative neoplasm, characterized by sustained thrombocytosis (≥450 x 10⁹/L), vasomotor symptoms and thrombotic / hemorrhagic complications. Treatment and prognosis relies on risk stratification, based on age and thrombosis history. Survival is similar to that of general population, however there is a low risk of transformation to myelofibrosis (MF) and acute myeloid leukemia (AML).

To describe demographic, clinical and hystopathologic characteristics, as well as general outcome of patients with ET treated at INCMNSZ.

Descriptive and retrospective study of patients with ET, diagnosed from January 2000 to December 2012 and reclassified according to WHO 2008 criteria. General data and overall survival were calculated using SPSS v17.0.

Forty-nine patients with ET were included, with a median age of 56 years, 65.3% were female. At diagnosis, 98% had an ECOG of 0 to 1, and 42.9% had three or more comorbidities. Table 1 shows laboratory parameters at diagnosis. Forty-nine percent and 16.3% were classified as having high risk according to Tefferi and IPSET classifications respectively. In 60.4% of biopsies, reticulin was not reported; in positive cases, grade 1 fibrosis was the most frequent in 20.8%. Karyotype was normal in 53.1%, and it was possible to determine JAK2 V617F mutation only in 16.4%, reported as positive in 8.2%. Thrombotic events were present in 16.3%, 50% of which were venous. Secondary Von Willebrand syndrome was documented in 10.2%. Hydroxyurea and acetylsalicylic acid were the most used drugs, 91.8% and 89.8% respectively, among others. Of patients who received treatment, 42.9% and 38.8% had partial and complete responses, respectively. Histological transformation was documented in 14.3%, 8.17% to MF and 6.12% to AML, at a median of 7.8 years from diagnosis. At last follow-up, 79.6% were alive, with median overall survival not reached, and 8.2% had died, mainly because of progression of MF/AML.

In this cohort thrombosis incidence is similar to international reports (11-25%), and the high rate of transformation to MF and AML perhaps is influenced by the diagnostic criteria used in the early 2000 (PVSG criteria vs WHO criteria). Concerning mutational status of JAK2 V617, the incidence is low and strong conclusions can not be made in this matter because of the retrospective sense of the study and the availability of the test in our center. In conclusion, these results emphasize the importance of adhering to strict clinical and histopatological criteria to diagnose patients with ET, establish the risk and identify those who do not require cytoreductive treatment, in order to reduce the risk of long term complications.

No relevant conflicts of interest to declare.