Long-Term Survival Data in 652 Patients with Primary Myelofibrosis or Polycythemia Vera— Trends in Recent Years.

Polycythemia vera (PV) and primary myelofibrosis (PMF) are stem cell-derived myeloproliferative neoplasms characterized clinically by increased red cell volume and bone marrow fibrosis, respectively. Phlebotomy is the cornerstone of treatment in PV whereas hydroxyurea has been the traditional drug of choice in both PV and PMF. Over the last 20 years, several new treatment approaches have been introduced and promoted (e.g. interferon-alpha, anagrelide, thalidomide, allogeneic stem cell transplantation) but their benefit in terms of survival has not been confirmed in controlled studies.

Study patients were recruited form the Mayo Clinic database for myeloproliferative neoplasms. Diagnosis was based on 2001 WHO criteria. Follow-up information was updated in July, 2009. In order to assess changes in survival over time, patients were stratified into two groups by year-of-diagnosis: 1970-1990 and 1991-2005. Survival analysis was performed by the Kaplan-Meier method and comparisons made by the log-rank test. Cox regression model was used for multivariable analysis.

652 patients were studied, including 314 with PMF (median age 57 years, range 18-88; 193 males) and 338 with PV (median age 63 years, range 18-93; 183 males). Overall median survivals were 6.5 years for PMF and 12.2 years for PV (p<0.0001); ten- and twenty-year survival rates were 37% and 13% in PMF and 60% and 18% in PV (Figure). Both the International Prognostic Scoring System for PMF (IPSS; Cervantes et al. Blood 2009;113:2895) and the age/leukocyte count-based PSS for PV (Gangat et al. BJH 2007;138:354) were validated in the current series of patients.

Considering all patients, there was no significant difference in survival when either PMF (p=0.91) or PV (p=0.73) patients were stratified according to year-of-diagnosis (Figure); median survivals were 4.7 and 6.6 years in PMF patients diagnosed 1970-1990 (n=54) and 1991-2005 (n=260), respectively; the corresponding median survival figures for PV were 11.8 (n=170) and 12.2 (n=168) years. These results did not change when adjusted for age and sex and, in PV, for age/leukocyte count-based PSS. In PMF, however, borderline significance (p=0.05) was noted when IPSS scores were introduced into the Cox model with further analysis showing improved survival in Int-2/high risk patients with PMF diagnosed after 1990 (p=0.01).

The current study provides mature survival data in PMF and PV using large cohorts of consecutive patients seen at a single institution. Although median survival is significantly better in PV compared to PMF, their survival curves converge after 20 years of follow-up, underscoring the poor long-term prognosis in PV patients. The study also suggests improved survival for high/intermediate-2 risk PMF in recent years.

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Off Label Use: hydroxyurea use in myelofibrosis.