Polycythemia vera in Chinese patients: thirty-six years of experience.

Forty-one patients with polycythemia vera (PV) according to the PVSG criteria were analysed retrospectively from January 1960 to March 1996. There were 23 male and 18 female patients with a median follow-up of 66.5 months (3-431 months). Median age was 62 (range: 37-85). The median hemoglobin level at diagnosis was 18.8 g/dl. Four patients were treated by venesection alone, 20 patients received hydroxyurea and intermittent venesection, 3 were treated with radioactive phosphorus alone, and 14 had both hydroxyurea and radioactive phosphorus. During the course of illness, 14 patients (34%) developed a total of 19 thrombotic events. Of the thrombotic events, 16 were arterial and 3 were venous. Two patients had both arterial and venous thrombosis sequentially. The probability of thrombosis-free survival after treatment was 83% at 10 years and 73% at 20 years. One patient developed post-polycythemic myeloid metaplasia 24 months after diagnosis. Of 17 patients exposed to radioactive phosphorus, only 1 developed secondary acute myeloid leukemia (AML) 9 years afterwards. Of the 20 patients treated with hydroxyurea for a median duration of 63.5 months (2-130 months), there is no case of secondary malignancy. Overall survival was 83% at 10 years and 62% at 20 years. In conclusion, PV in Chinese is a relatively benign disease with a low risk of thrombosis as compared to Caucasian patients. Hydroxyurea has a very low risk of secondary leukemia and is a safe drug to use in Chinese patients with PV.