Objective: To explore the survival and the risk factors of poor prognosis in Chinese patients with polycythemia vera (PV).
Methods: A total of 816 patients with a definite diagnosis of PV were enrolled from August 1983 to June 2013 into this study. The standardized mortality ratio (SMR) was calculated by comparing the cumulative survival of 816 PV patients with age- and sex- and calendar year-matched healthy Chinese population from the national bureau of statistics of the People's Republic of China. The clinical features of diagnosis and prognosis of PV patients were analyzed by Cox regression to identify risk factors for the poor prognosis of PV and to develop a dynamic prognostic model in Chinese patients. The effects of different treatments on the development of acute myelocytic leukemia (AML) and post-PV myelofibrosis (post-PV MF) were determined by Kaplan-Meier analysis. JAK2 V617F allele burden (V617F%) was determined by quantitative real-time PCR in 104 patients.
Results: The median follow-up time was 6 (1-42) years. The 10-, 15- and 20-year overall survival (OS) was 89.50%, 76.70% and 64.70%, respectively. The SMR was 17.40 (95% CI: 13.71-21.78). Cox regression analysis revealed that white blood cell (WBC) count>10×10(9)/L (HR=3.10, 95% CI: 1.47-6.53, P=0.003), age>60 years (HR=2.89, 95% CI: 1.84-4.53, P<0.001) and prior thrombosis (HR=2.66, 95% CI: 1.65-4.29, P<0.001) were significant predictors for the poor prognosis of PV. Based on the hazard radio, 816 patents were allocated into 4 categories with significantly different survival: low (sum of points=0; median survival no reached), intermediate 1 (sum of points=1; median survival 33.10 (28.20-38.00) years), intermediate 2 (sum of points=2; median survival 23.00 (16.08-29.92) years), high (sum of points=3; median survival 13.00 (10.58-15.42) years). The mortality of high risk group was 5.37 fold higher than low risk patients. The 10- and 20-year survival of no post-PV MF were 89.50% and 79.60%, respectively, for interferon α (IFN-α); 73.80% and 43.50%, respectively, for hydroxyurea treatment; 82.20% and 71.40%, respectively, for alkylating agent treatment; and 80.00% and 38.20%, respectively, for no cytoreductive treatment. The treatment of exposure to IFN-α associated with a higher rate of no-post-PV MF survival (Log-rank=9.79, P=0.020). There were more post-PV MF patients with V617F%≥50% compared with those V617F%<50% (P<0.001).
Conclusions: The mortality of PV patients is significantly higher than that of healthy Chinese population. The WBC count>10×10(9)/L, age>60 years, and prior thrombosis are identified as significant predictors for the prognosis of PV. The risk of post-PV MF transformation may be ameliorated by IFN-α via decreasing the burden of JAK2 V617F mutation.